@misc{FellahHezilSamadetal., author = {Fellah, Mamoun and Hezil, Naouel and Samad, Mohammed Abdul and Djellabi, Ridha and Montagne, Alex and Mejias, Alberto and Kossman, Stephania and Iost, Alain and Purnama, Agung and Obrosov, Aleksei and Weiß, Sabine}, title = {Effect of Molybdenum Content on Structural, Mechanical, and Tribological Properties of Hot Isostatically Pressed β-Type Titanium Alloys for Orthopedic Applications}, series = {Journal of Materials Engineering and Performance}, volume = {28}, journal = {Journal of Materials Engineering and Performance}, number = {10}, issn = {1059-9495}, doi = {10.1007/s11665-019-04348-w}, pages = {5988 -- 5999}, abstract = {Aiming to develop alloys with better properties for orthopedic applications, the focus of the present research was to evaluate the effect of Mo at.\% content on structural, mechanical, and tribological properties of hot isostatically pressed Ti-xMo (x = 4, 8, 12, 15, and 20 at.\%) alloys. The structural evolution, mechanical properties, and tribological behavior of the nanostructured Ti-xMo alloys were evaluated using x-ray diffraction, scanning electron microscope, and ball-on-disk tribometer. Wear tests were conducted under different applied loads of 2, 8, and 16 N. Experimental results indicated that the structural evolution and morphological changes of the milled alloys were sensitive to their molybdenum (Mo) content. The morphological characterization showed that the crystallite size and the particle size decreased with increasing Mo content (at.\%) reaching the lowest values of 27 and 26 nm in the case of Ti-15Mo and Ti-20Mo, respectively. On the other hand, the coefficient of friction and wear rates were found to be decreasing with increasing Mo content.}, language = {en} } @misc{ObrosovKashkarovSharmaetal., author = {Obrosov, Aleksei and Kashkarov, Egor B. and Sharma, A. and Weiß, Sabine}, title = {Microstructure and defect structure of Zr-1Nb alloy deep surface modified by high Intensity Ti Ion implantation}, series = {MC Microscopy Conference, 01-05 September 2019, Berlin, Abstracts}, journal = {MC Microscopy Conference, 01-05 September 2019, Berlin, Abstracts}, address = {Berlin}, pages = {86}, abstract = {A deep surface modified TiZr layer was fabricated by high-intensity low-energy titanium ion implantation into zirconium alloy Zr-1Nb alloy with the various dose in the range of (5.4-9.56) × 1020 ion/cm2. The gradient distribution of titanium as well as vacancy type defects were analysed. The effects of ion implantation on microstructure, phase composition and elemental distribution of TiZr layer were analysed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and glow-discharge optical emission spectroscopy, respectively. The results show the appearance of Zr-Ti intermetallic phases of different stoichiometry after Ti implantation. The intermetallic phases are transformed from both Zr0.7Ti0.3 and Zr0.5Ti0.5 to single Zr0.6Ti0.4 phase with the increase in the implantation dose. The depth of Ti penetration into the bulk of Zr increases from 6 to 13 μm with the implantation dose. The higher current density (170 mA/cm2) leads to the increase in the grain size and surface roughness. It was revealed that TiZr layer (~10 μm thickness) is represented by α′ + α(TiZr) lamellar microstructure with gradient distribution of Ti through the layer depth. Transmission electron microscopy was used for investigation of the physical basis of Ti diffusion and its influence on the evolution of the defect structure after surface modification. Furthermore, it was found that on the surface between substrate and implanted layer was found an amorphous layer, which occur as a result of further stress accumulations from the higher implantation doses.}, language = {en} } @misc{FellahHezilDekhiletal., author = {Fellah, Mamoun and Hezil, Naouel and Dekhil, Leila and Samad, Mohammed Abdul and Djellabi, Ridha and Kosman, Stephania and Montagne, Alex and Iost, Alain and Obrosov, Aleksei and Weiß, Sabine}, title = {Effect of sintering temperature on structure and tribological properties of nanostructured Ti-15Mo alloy for biomedical applications}, series = {Transactions of Nonferrous Metals Society of China}, volume = {29}, journal = {Transactions of Nonferrous Metals Society of China}, number = {11}, issn = {1003-6326}, doi = {10.1016/S1003-6326(19)65137-X}, pages = {2310 -- 2320}, abstract = {The effect of sintering temperature (1073-1373 K) on the structural and tribological properties of nanostructured ball-milled β-type Ti-15Mo samples was investigated. The prepared samples were characterized using various apperatus such as X-ray diffractometer, scanning electron microscope (SEM) and ball-on-plate type oscillating tribometer. Wear tests were conducted under different applied loads (2, 8 and 16 N). Structural results showed that the mean pore and crystallite size continuously decreased with increasing sintering temperature to reach the lowest values of 4 nm and 29 nm at 1373 K, respectively. The relative density of the sintered sample at 1373 K was as high as 97.0\%. Moreover, a higher sintering temperature resulted in higher relative density, greater hardness and elastic modulus of the sample. It was observed that both the friction coefficient and wear rate were lower in the sample sintered at 1373 K which was attributed to the closed porosity.}, language = {en} } @misc{ErmilovaKazakWeiss, author = {Ermilova, Evgeniia and Kazak, Fedor and Weiß, Sabine}, title = {Stability of structured sheet metals during buckling}, series = {Materials Testing}, volume = {61}, journal = {Materials Testing}, number = {10}, issn = {2195-8572}, doi = {10.3139/120.111403}, pages = {929 -- 935}, abstract = {Structured materials can be a progressive alternative to commonly used flat sheets. There is an enormous range of possibilities for using structured sheet metals due to their better stability. However, the effective use of these materials as well as their implementation in production requires precise knowledge about specific properties of structured sheet metals. The aim of this work is to obtain new knowledge about stiffness and stability during the deformation of this material. The structured sheet metals were investigated by means of buckling tests. The steel type investigated is a commonly used deep-drawing steel DC04. Six types of structure arrangements were compared to non-structured (flat) specimens as a reference. The influence of the type of structure arrangement as well as the deformation speed on the mechanical properties was investigated.}, language = {en} } @misc{FellahHezilDekhiletal., author = {Fellah, Mamoun and Hezil, Naouel and Dekhil, Leila and Samad, Mohammed Abdul and Montagne, Alex and Mejias, Alberto and Iost, Alain and Obrosov, Aleksei and Weiß, Sabine}, title = {Structural characterization of developed near β-Type Titanium Alloys (Ti-25NbxZr) for biomedical Applications}, series = {3rd International Conference on Mechanics and Materials : ICMM'2019 11-12 November 2019. Setif, Algeria, Abstracts book}, journal = {3rd International Conference on Mechanics and Materials : ICMM'2019 11-12 November 2019. Setif, Algeria, Abstracts book}, address = {Setif, Algeria}, pages = {224 -- 225}, abstract = {The osteoarthritis and degenerative diseases osteoporosis as well as trauma lead to the bone mechanical properties degradation due to absence of normal biological self healing processes or excessive loading [1-5]. These problems solution are artificial biomaterials, as surgical implantation of appropriate shapes helps restore function for the otherwise functionally compromised structures [1-5]. Biocompatibility is considered to be optimal once tissue neoformation and later function occurs around implantable devices [6]. The efficacy of biomaterials implants is determined mostly by their surface characteristics such as microstructure, surface morphology, composition and biological properties [2]. Aiming to develop alloys with better properties for orthopedic applications, the focus of the present research was to evaluate the effect of Zr at. \% content on structural, mechanical and tribological properties of hot isostatically pressed Ti-25Nb-xZr (x = 5, 10, 15, 20 and 25 at. \%) alloys. The structural evolution, and mechanical properties of the nanostructured Ti-Nb-xZr alloys were evaluated using X-Ray diffraction, scanning electron microscope. The mechanical properties were performed using Vickers hardness and berkovich nanoindentation. Experimental results indicated that the structural evolution and morphological changes of the milled alloys were sensitive to their Zirconium (at. \%) content. The morphological characterization showed that the crystallite size and the particle size decreased with increasing Zr content (at. \%). As well, as the Zr was added to the Ti-25NbXZr system, there was a clear decrease in the Vickers hardness and young's modulus. On the other hand, the coefficient of friction and wear rates were found to be decreasing with increasing Zr content.}, language = {en} } @misc{KhalilFellahHeziletal., author = {Khalil, S. and Fellah, Mamoun and Hezil, Naouel and Smata, L. and Montagne, Alex and Mejias, Alberto and Kossman, Stephania and Iost, Alain and Obrosov, Aleksei and Weiß, Sabine}, title = {Synth{\`e}se et caract{\´e}risation structurale d'un compos{\´e} nanostructur{\´e} de Ti, Mo et Zr pour applications biom{\´e}dicales}, series = {3rd International Conference on Mechanics and Materials : ICMM'2019 11-12 November 2019. Setif, Algeria, Abstracts book}, journal = {3rd International Conference on Mechanics and Materials : ICMM'2019 11-12 November 2019. Setif, Algeria, Abstracts book}, address = {Setif, Algeria}, pages = {243 -- 244}, abstract = {Le milieu m{\´e}dical est un perp{\´e}tuel demandeur de biomat{\´e}riaux compatibles surtout en orthop{\´e}die. Effectivement le nombre important d'arthroplasties effectu{\´e}es chaque ann{\´e}e ne cesse d'augmenter dans le monde, non seulement du fait vieillissement de la population ({\`a} partir de 65 ans), mais aussi de demandes de patients plus jeunes entre 45 ans et 55 ans. Actuellement, les compos{\´e}s {\`a} base de titane Ti sont largement utilis{\´e}s comme des biomat{\´e}riaux pour leur biocompatibilit{\´e}, leur r{\´e}sistance {\`a} la corrosion et leur faible module d'{\´e}lasticit{\´e}. Le molybd{\`e}ne et le zirconium sont parmi les meilleurs {\´e}l{\´e}ments alli{\´e}s parce qu'ils sont non toxiques et non allergiques et offrent d'excellentes propri{\´e}t{\´e}s. De plus,Le Zr peut augmenter la trempabilit{\´e} et la r{\´e}sistance {\`a} la corrosion de l'alliage . Mo est un {\´e}l{\´e}ment fort stabilisant pour la phase des alliages de titane et les alliages {\`a} base de Ti-Mo pr{\´e}sentent des propri{\´e}t{\´e}s m{\´e}caniques ad{\´e}quates compatibilit{\´e} et bonne cyto-compatibilit{\´e} . Par cons{\´e}quent, le syst{\`e}me Ti-Mo-Zr, qui a montr{\´e} une bonnes performances et de magnifiques perspectives dans l'application de biomat{\´e}riaux, a {\´e}t{\´e} intensivement{\´e}tudi{\´e} [1,2,3]. Cependant, les alliages de Ti largement utilis{\´e}s, tels que les interstitiels extra-low (ELI) Ti-6Al-4V (wt.\% en poids ), Ti- 5Al-2,5 Fe et Ti-6Al-7Nb, ont le risque de lib{\´e}rer de l'aluminium toxique (Al) et les Ions de vanadium (V) in vivo, ce qui peut causer des probl{\`e}mes de sant{\´e}, comme la maladie d'Alzheimer et la neuropathie[4].La m{\´e}tallurgie des poudres (MP), y compris la m{\´e}thode de mixture des composants en poudre, qui consiste {\`a} fritter titane en poudre ou ses m{\´e}langes avec d'autres composants en poudre, est un proc{\´e}d{\´e} {\´e}conomique {\`a} moindre cout. La nanotechnologie est intervenue dans la structuration des biomat{\´e}riaux {\`a} l'{\´e}chelle nanom{\´e}trique (entre1nmet 100 nm) par soucis d'am{\´e}lioration des propri{\´e}t{\´e}s m{\´e}canique surtout le module de Young.}, language = {fr} } @misc{ShapovalovGaalHoenigetal., author = {Shapovalov, Oleg and Gaal, Mate and H{\"o}nig, Gerald and Gradt, Thomas and Weiß, Sabine}, title = {Temperature dependence of the propagation speed of a longitudinal wave in different solids for use as a wedge material in an extreme-temperature-resistant ultrasonic transducer}, series = {Proceedings of the 23rd International Congress on Acoustics : integrating 4th EAA Euroregio 2019 : 9-13 September 2019 in Aachen, Germany}, volume = {2019}, journal = {Proceedings of the 23rd International Congress on Acoustics : integrating 4th EAA Euroregio 2019 : 9-13 September 2019 in Aachen, Germany}, editor = {Ochmann, Martin and Vorl{\"a}nder, Michael and Fels, Janina}, address = {Aachen}, isbn = {978-3-939296-15-7}, issn = {2226-7808}, doi = {10.18154/RWTH-CONV-239953}, pages = {4754 -- 4760}, abstract = {In special cases of angle beam ultrasonic measurement - e.g. defect detection in hot solids as well as flow measurement of liquid gases or energy storage mediums [1] - the applied transducer has to withstand extreme temperatures. Since the irradiation angle into the specific material is determined not only by wedge design, but also by the speed of sound in both the wedge material and the tested object, the developer must take into account the speed of the wave propagation in a wedge material over the whole temperature range of transducers application. In this study we investigate the temperature dependence of the speed of longitudinal wave propagation in 10 different materials in the range from -200 °C to 400 °C. The investigated materials belong to different material classes (ceramics, glass, as well as ferrous and non-ferrous metals) and are all temperature-resistant up to at least 600 °C, and therefore applicable as wedge materials in an ultrasonic transducer for use at extreme temperatures.}, language = {en} } @misc{MarchenkoYasenchukGuntheretal., author = {Marchenko, Ekaterina and Yasenchuk, Yuri and Gunther, Sergey and Baigonakova, Gulsharat and Gunther, Victor and Chekalkin, Timofey and Weiß, Sabine and Obrosov, Aleksei and Dubovikov, Kirill}, title = {Structural-phase surface composition of porous TiNi produced by SHS}, series = {Materials Research Express}, volume = {6}, journal = {Materials Research Express}, number = {11}, issn = {2053-1591}, doi = {10.1088/2053-1591/ab4e32}, pages = {12}, abstract = {The study aimed to characterize the structural-phase composition of the porous SHS TiNi surface explored by the GIXRD method. The surface layers at a depth of up to 100 nm mainly consist of amorphous nanocrystalline intermetallic oxycarbonitrides Ti₄Ni₂(O,N,C) with nonmetallic inclusions of different structural variants and routes of origin. Fine-porous alloys were synthesized at ignition temperatures of 450-480 °C. A distinct feature of the surface of crystalline phases therein was shown to be a low degree of crystallinity (up to 40\%) and presence of multifarious glass and cermet phases evident as NiSi₂, NaAlSiO (SO₄), SiO₂, MgSi₂, and CaCO₃. Conversely, large-pore alloys ignited at temperatures of 280-330 °C have a higher degree of crystallinity (up to 70\%). An individually selected GIXRD technique and precision structural phase analysis are capable to determine a set of other superficial nonmetallic and cermet phases reported as CaTiO₃, Si (P2O₇), CaSiO₃, MgAl₂O₄, TiNiAl, as well as the Ti₃SiC₂MAX phase.}, language = {en} } @misc{FellahHezilSamadetal., author = {Fellah, Mamoun and Hezil, Naouel and Samad, Mohammed Abdul and Touhami, Mohamed Zine and Montagne, Alex and Iost, Alain and Obrosov, Aleksei and Weiß, Sabine}, title = {Preliminary investigation on the bio-tribocorrosion behavior of porous nanostructured β-type titanium based biomedical alloys}, series = {Materials Letters}, volume = {257}, journal = {Materials Letters}, issn = {0167-577X}, doi = {10.1016/j.matlet.2019.126755}, pages = {4}, abstract = {The bio-tribocorrosion behavior of newly developed near β-types Ti-15Nb and Ti-15Mo alloys was investigated in Phosphate-Buffered Saline (PBS) under different loads. Open-Circuit Potential (OCP), friction coefficient, wear volume and wear rate were evaluated. The results revealed that Ti-15Nb alloy exhibited lower wear rate, lower friction coefficient and better corrosion resistance during tribocorrosion than the Ti-15Mo alloy. This can be attributed to the diffusion of Nb which increases the repassivation rate (formation of a protective layer) in the Ti-15Nb alloy. In contrast Ti-15Mo shows a significantly higher rate of chemical reaction.}, language = {en} } @misc{FellahHezilTouhamietal., author = {Fellah, Mamoun and Hezil, Naouel and Touhami, Mohamed Zine and Obrosov, Aleksei and Weiß, Sabine and Kashkarov, Egor B. and Lider, Andrey M. and Montagne, Alex and Iost, Alain}, title = {Enhanced Structural and Tribological Performance of Nanostructured Ti-15Nb Alloy for Biomedical Applications}, series = {Results in Physics}, volume = {15}, journal = {Results in Physics}, issn = {2211-3797}, doi = {10.1016/j.rinp.2019.102767}, pages = {7}, abstract = {Low modulus β-type Ti-15Nb alloys were prepared by subjecting them to different sintering temperatures (800, 900, 1000 and 1100 °C) and their morphological and structural properties were evaluated. X-ray diffraction analysis was used for the morphological characterization which indicated that the mean pore and crystallite size continuously decreased with increasing sintering temperature to reach the lowest values of 41 nm and 27.5 nm at 1100 °C, respectively. Moreover, the higher sintering temperature resulted in higher relative density, greater hardness and young's modulus of the Ti-15Nb alloys. Wear tests were conducted using a ball-on-plate type Oscillating tribometer, under different applied loads (2, 8 and 16 N) to evaluate their tribological characterization. The wear rate and friction coefficient were lower at higher sintering temperature. This enhancement in tribological properties was attributed to a grain refinement. The Ti-15Nb alloys sintered at 1100 °C showed the best tribological performance.}, language = {en} } @misc{StendalBambachEisentrautetal., author = {Stendal, Johan Andreas and Bambach, Markus and Eisentraut, Mark and Sizova, Irina and Weiß, Sabine}, title = {Applying Machine Learning to the Phenomenological Flow Stress Modeling of TNM-B1}, series = {Metals}, volume = {9}, journal = {Metals}, number = {2}, issn = {2075-4701}, doi = {10.3390/met9020220}, pages = {18}, abstract = {Data-driven or machine learning approaches are increasingly being used in material science and research. Specifically, machine learning has been implemented in the fields of materials discovery, prediction of phase diagrams and material modelling. In this work, the application of machine learning to the traditional phenomenological flow stress modelling of the titanium aluminide (TiAl) alloy TNM-B1 (Ti-43.5Al-4Nb-1Mo-0.1B) is investigated. Three model types were developed, analyzed and compared; a physics-based phenomenological model (PM) originally developed for steel by Cingara and McQueen, a purely data-driven machine learning model (MLM), and a hybrid model (HM), which uses characteristic points predicted by a learning algorithm as input for the phenomenological model. The same amount of data was used to both fit the PM and train the MLM and HM. The models were analyzed and compared based on the accuracy of their predictions, development and computing time, and their ability to predict on interpolated and extrapolated inputs. The results revealed that for the same amount of experimental data, the MLM was more accurate than the PM. In addition, the MLM was better able to capture the characteristic peak stress in the TNM-B1 the flow curves, and could be developed and computed faster. Furthermore, the MLM was able to make realistic predictions for inputs outside the experimental data used for training. The HM showed comparable accuracy to the PM for the experimental conditions. However, the HM was able to produce a better fit for input conditions outside the training data.}, language = {en} } @misc{EisentrautBolzSizovaetal., author = {Eisentraut, Mark and Bolz, Sebastian and Sizova, Irina and Bambach, Markus and Weiß, Sabine}, title = {Development of a heat treatment strategy for the γ-TiAl based alloy TNM-B1 to increase the hot workability}, series = {SN Applied Sciences}, volume = {1}, journal = {SN Applied Sciences}, number = {11}, issn = {2523-3963}, doi = {10.1007/s42452-019-1563-4}, pages = {8}, language = {en} } @misc{StendalEisentrautSizovaetal., author = {Stendal, Johan Andreas and Eisentraut, Mark and Sizova, Irina and Bolz, Sebastian and Bambach, Markus and Weiß, Sabine}, title = {Effect of heat treatment on the workability of hot isostatically pressed TNM-B1}, series = {AIP Conference Proceedings}, volume = {2113}, journal = {AIP Conference Proceedings}, number = {1}, isbn = {978-0-7354-1847-9}, doi = {10.1063/1.5112544}, language = {en} } @incollection{FellahHezilAbderrahimetal., author = {Fellah, Mamoun and Hezil, Naouel and Abderrahim, Karima and Samad, Mohammed Abdul and Montagne, Alex and Mejias, Alberto and Iost, Alain and Kossman, Stephania and Chekalkin, Timofey and Obrosov, Aleksei and Weiß, Sabine}, title = {Investigating the Effect of Sintering Temperature on Structural and Tribological Properties of a Nanostructured Ti-20Nb-13Zr Alloy for Biomedical Applications}, series = {Characterization of Minerals, Metals, and Materials}, booktitle = {Characterization of Minerals, Metals, and Materials}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-36628-5}, issn = {2367-1181}, doi = {10.1007/978-3-030-36628-5_61}, pages = {619 -- 629}, abstract = {β-type Ti-20Nb-13Zr alloys with low Young's modulus were prepared at different sintering temperatures (950, 1050, 1150, and 1250 °C). The morphological and structural characteristics of as-prepared samples were investigated by several methods. Wear tests were conducted using a ball-on-plate type oscillating tribometer under different applied loads (2, 10, and 20 N). The morphological characterization indicated that the mean pore and crystallite size continuously decreased with increasing sintering temperature to reach lowest values of 40 nm and 38 nm at 1250 °C, respectively. The relative density of the 1250 °C sintered sample was as high as 98.7\%. Moreover, the higher sintering temperature resulted in higher relative density and closed porosity of the sample. Both the friction coefficient and wear rate were lower in the sample sintered at 1250 °C as compared to other samples. This enhancement in tribological properties was attributed to a closed porosity.}, language = {en} } @misc{FellahHezilTouhamietal., author = {Fellah, Mamoun and Hezil, Naouel and Touhami, Mohamed Zine and Hussien, Mohammed A. and Montagne, Alex and Mejias, Alberto and Iost, Alain and Kossman, Stephania and Chekalkin, Timofey and Obrosov, Aleksei and Weiß, Sabine}, title = {Effect of Sintering Temperature on Mechanical and Tribological Behavior of Ti-Ni Alloy for Biomedical Applications}, series = {TMS 2020 149th Annual Meeting \& Exhibition Supplemental Proceedings}, journal = {TMS 2020 149th Annual Meeting \& Exhibition Supplemental Proceedings}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-36295-9}, issn = {2367-1181}, doi = {10.1007/978-3-030-36296-6_157}, pages = {1701 -- 1710}, abstract = {Ti-Ni powder compacts were prepared by mechanical alloying (MA), followed by hot isostatic pressing (HIP). Afterwards, the samples were sintered at different temperatures (950, 1050, 1150 and 1250 °C). Microhardness, density, crystallite size as well as microstrain of the sintered samples were measured and analyzed. Wear characteristics in phosphate-buffered saline (PBS) solution was tested under different applied loads of 2 N, 10 N, and 20 N, respectively. The results indicated that the crystallite size continuously decreases with increasing sintering temperature and reaches the lowest value of 31.3 nm at 1250 °C. The relative density of the sample sintered at 1250 °C is 98.0\%. Moreover, the higher sintering temperatures lead to the higher relative density and the increase in hardness and young's modulus of the sample. At the same time the friction coefficient and wear rate were lower for the samples sintered at 1250 °C. This improvement in friction and wear resistance is attributed to the grain size refinement. Ti-Ni sintered at 1250 °C showed good tribological performance under all test conditions.}, language = {en} } @misc{HezilFellahMontagneetal., author = {Hezil, Naouel and Fellah, Mamoun and Montagne, Alex and Iost, Alain and Obrosov, Aleksei and Weiß, Sabine}, title = {Removal of Chromium (VI) from Water onto Activated Carbon by Adsorption in Dynamic Mode}, series = {TMS 2020 149th Annual Meeting \& Exhibition Supplemental Proceedings}, journal = {TMS 2020 149th Annual Meeting \& Exhibition Supplemental Proceedings}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-36295-9}, issn = {2367-1181}, doi = {https://doi.org/10.1007/978-3-030-36296-6_80}, pages = {855 -- 863}, abstract = {Hexavalent chromium pollution from industrial waste water is a serious problem as it can cause adverse effects on the environment. Several methods are used to reduce the harmful effects of this pollutant, especially physico-chemical methods, such as adsorption technology. The present study aims to remove Cr (VI) from industrial sources in a fixed-bed column of activated carbon. The experiments were carried out at natural pH and temperature with a flow rate (5, 10, and 20 mL/min) and bed height (3.5 cm). Breakthrough curves for feed concentrations (0.01, 0.03, and 0.05 mol/L) were investigated. The results indicated a marked decrease up to 99\%. The value of the flow constant for the Thomas model decreased with the increase in the concentration of the incoming substance, but increased with the increase in the flow rate.}, language = {en} } @misc{EvdokimovDoynovOssenbrinketal., author = {Evdokimov, Anton and Doynov, Nikolay and Ossenbrink, Ralf and Obrosov, Aleksei and Weiß, Sabine and Michailov, Vesselin}, title = {Thermomechanical laser welding simulation of dissimilar steel-aluminum overlap joints}, series = {International Journal of Mechanical Sciences}, volume = {190}, journal = {International Journal of Mechanical Sciences}, issn = {1879-2162}, doi = {10.1016/j.ijmecsci.2020.106019}, pages = {18}, abstract = {Mixing of steel and aluminum within the weld pool during keyhole laser welding results in a complex dissimilar microstructure, which in turn, initiates a shift in weld metal mechanical properties. In this study, a numerical model for computation of distortions in laser-welded dissimilar overlap joints (austenitic stainless steel 304 - 6082-T6 aluminum alloy), which considers properties of the mixed steel-aluminum weld metal was developed. The required yield strength, Young's modulus, and strain hardening exponent of the weld metal were experimentally determined using the indentation technique coupled with energy-dispersive X-ray spectroscopy. The designed material model calculates the weld elastic-plastic properties as a function of the aluminum concentration. The softening of the alloys in the heat-affected zone was determined by physical simulations and considered as a function of maximum temperature. Computed and measured distortions showed good agreement for various welding regimes with an average deviation of 18.4\%. The sensitivity analyses indicated that the application of the developed weld material model significantly improves the accuracy of the thermomechanical simulations.}, language = {en} } @misc{BaigonakovaMarchenkoChekalkinetal., author = {Baigonakova, Gulsharat and Marchenko, Ekaterina and Chekalkin, Timofey and Kang, Ji-hoon and Weiß, Sabine and Obrosov, Aleksei}, title = {Influence of Silver Addition on Structure, Martensite Transformations and Mechanical Properties of TiNi-Ag Alloy Wires for Biomedical Application}, series = {Materials}, volume = {13}, journal = {Materials}, number = {21}, issn = {1996-1944}, doi = {10.3390/ma13214721}, pages = {11}, abstract = {The microstructural and functional behavior of TiNi-based wires with a silver content of 0-1.5 at.\% was evaluated. The concentration range for Ag doping determined for the TiNi wires with potential for the medical industry was 0-0.2 at.\%. Microstructure analysis of TiNi wires with different silver contents at room temperature indicated a multiphase structural state. Various internal structures with tangled grain boundaries were formed by intense plastic deformation. The nanocrystalline structure and phase state of wire with the minimum silver content (0.1 at.\% Ag) provide full shape recovery, the greatest reversible strain, and optimal strength and ductility. TiNi ingots with a high Ag content (0.5-1.5 at.\%) cracked under minimum load due to excess silver that crystallized along the grain boundaries and broke cohesion bonds between the TiNi grains.}, language = {en} } @misc{HazilFellahMontagneetal., author = {Hazil, Naouel and Fellah, Mamoun and Montagne, Alex and Iost, Alain and Obrosov, Aleksei and Weiß, Sabine}, title = {Study of the photocatalytic degradation of Orange methyl dye in the presence of titanium dioxide}, series = {La Troisi{\`e}me Conf{\´e}rence M{\´e}diterran{\´e}enne de la Biodiversit{\´e} 2019 (BIODIV 2019)}, journal = {La Troisi{\`e}me Conf{\´e}rence M{\´e}diterran{\´e}enne de la Biodiversit{\´e} 2019 (BIODIV 2019)}, publisher = {L'ASCOB-SYRTIS}, address = {Hammamet, Tunisie}, pages = {105}, abstract = {The use of photocatalytic techniques for water purification and wastewater treatment is very widespread, in our work we used TiO2 to photocatalyrate orange methyl (MO). In addition, the effects of some parameters on photodegradation of MO have been studied, such as the presence and / or absence of light (UV). The use of TiO2 showed a high MO degradation efficiency of up to 98\%. The presence of H2O2 in the photocatalytic reaction may favor the photocatalytic degradation efficiencies. In addition, the experimental results have demonstrated an excellent rate of the order of 99\%.}, language = {en} } @misc{PrechavutWeiss, author = {Prechavut, Ananya and Weiß, Sabine}, title = {Analyse der Korrosionsprodukte eines im CO2 Methanisierungsprozess verwendeten Edelstahlflansches aus 316L}, abstract = {Die Weltklimakonferenz fordert eine massive Senkung der Treibhausgasemissionen mittels Abkehr von der Nutzung fossiler Brennstoffe hin zur Verwendung umweltvertr{\"a}glich hergestellter Energie. Da erneuerbare Energien aber bisher nicht durchweg bedarfsgerecht zur Verf{\"u}gung stehen und schlecht speicherbar sind, besteht eine kurzfristige L{\"o}sungsm{\"o}glichkeit in Umwandlung, Speicherung und Wiederverwendung klimasch{\"a}dlicher Verbrennungsgase. Eine effiziente L{\"o}sung zur Nutzung von CO2 ist dessen Umwandlung in ein speicherbares, zur Energieerzeugung nutzbares Gas. Mit der Methanisierung von CO2 kann eine erhebliche Reduzierung der Treibhausgasemissionen erreicht werden, wenn Methanschlupf vermieden wird. Bei dieser sogenannten Sabatier-Reaktion, die normalerweise bei 350°C bis 600°C stattfindet, reagiert Kohlendioxid mit Wasserstoff zu Methan. Als Reaktionsprodukte treten außer Methan und Wasser die Rest-Reaktanten sowie kleine Mengen an Verunreinigungen aus dem Verbrennungsprozess auf. Reaktionsbeh{\"a}lter und Leitungen bestehen {\"u}blicherweise aus Edelstahl. Durch hohe Umgebungs-temperatur und aggressive Umgebungsmedien kann auch bei dem normalerweise temperatur- und korrosionsbest{\"a}ndigen Werkstoff 316L Korrosion auftreten, Materialeigenschaften beeinflussen und zu Materialversagen f{\"u}hren. Zur Bewertung des Einflusses des CO2 Methanisierungs-Prozesses auf 316L wurde ein Methanisierungs-Reaktor im Labormaßstab nach der Nutzung demontiert und untersucht. In verschiedenen Bauteilen des Reaktors (Gaszuleitung, Gasaustritt, Reaktorsegment) wurden Korrosionsbel{\"a}ge gefunden. Abh{\"a}ngig von ihrer Lage im Bauteil sind diese Korrosionsschichten sehr unterschiedlich aufgebaut. Mikrostruktur und Elementzusammensetzung der Schichten wurden mittels Rasterelektronenmikroskopie kombiniert mit energiedispersiver R{\"o}ntgenspektroskopie analysiert. W{\"a}hrend die Gaszuleitung nur moderaten Korrosionsangriff zeigt konnten im Bereich des Gasaustritts Spalt-, Kontakt- und Lochkorrosion nachgewiesen werden. Innerhalb der Korrosions¬schichten wurden drei Zonen (Mehrschichtenstruktur, Partikelansammlung und br{\"u}chiger Passivfilm) identifiziert. Die Mehrschichtzone setzt sich aus kolumnaren und granularen Strukturen zusammen, die Partikelansammlungen bestehen aus zylinderf{\"o}rmigen und kugelf{\"o}rmigen Partikeln. Die Elementzusammensetzung innerhalb der Korrosionsschichten l{\"a}sst auf Kontaktkorrosion verursacht durch das Material der Dichtringe schließen.}, language = {de} } @misc{PrechavutWeiss, author = {Prechavut, Ananya and Weiß, Sabine}, title = {Corrosion Analysis of a 316L Stainless Steel Gas Outlet Sealed with a Copper Ring Used in the CO2 Methanation Process}, pages = {1}, abstract = {The central commitment of the 2015 World Climate Conference is to limit geothermal heating by massively reducing greenhouse gas emissions by decreasing the use of fossil fuels and promoting environmentally friendly energy. However, since renewable energies have so far not been available as required and are difficult to store, there is a short-term solution in the conversion, storage and reuse of climate-damaging combustion gases. An efficient solution for using CO2 is to convert it into a gas that can be stored and used to generate energy. With the so-called "power-to-gas technology", a significant reduction in greenhouse gas emissions can be achieved by methanation of CO2 if methane slip is avoided. Methanation is a chemical reaction in which carbon dioxide reacts with hydrogen to methane. This transformation, which normally takes place at 350 ° C to 600 ° C, is also known as the Sabatier reaction. In addition to methane and water, the remaining reactants such as carbon dioxide, hydrogen, oxygen and nitrogen as well as small amounts of impurities from the combustion process, occur as reaction products. Reaction containers and lines are usually made of stainless steel. Due to high ambient temperature and aggressive ambient media, corrosion can also occur with the generally temperature and corrosion-resistant 316L material, influence material properties and lead to material failure. To assess the influence of the CO2 methanation process on 316L, a laboratory-scale methanation reactor was fractioned and examined after use. Corrosion deposits were found in various components of the reactor (gas supply line, gas outlet, reactor segment). Depending on their position within the component, these corrosion layers are structured very differently. Microstructure and element composition of the layers were analyzed using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy. While the gas supply shows only moderate corrosion attack, crevice, contact- and pitting corrosion were detected in the corroded area of the gas outlet. Three zones (multilayer structure, particle accumulation and brittle passive film) were identified within the corrosion layers. The multi-layer zone is composed of columnar and granular structures, the particle accumulations consist of cylindrical and spherical particles. The element composition within the corrosion layers suggests contact corrosion caused by the material of the sealing rings.}, language = {en} } @misc{EisentrautStendalBolzetal., author = {Eisentraut, Mark and Stendal, Johan Andreas and Bolz, Sebastian and Bambach, Markus and Weiß, Sabine}, title = {Applying a softening adapted acceleration to the hot deformation of TNM-B1}, series = {MRS Fall Meeting 2020}, journal = {MRS Fall Meeting 2020}, abstract = {Hot isostatically forged TiAl turbine blades made of TNM-B1 are commercially used in aircraft engines, as they offer significantly lower weight than the traditional nickel-based blades while exhibiting similar strength. Like other TiAl alloys, TNM-B1 displays high peak stress followed by a strong softening behavior (i.e. stress reduction) during hot deformation. This softening can be used to accelerate the deformation process by reducing the processing time and in turn the costs for TNM-B1 parts. In order to avoid increased damage during the accelerated process, a pre-heat treatment (HT) for the hot isostatically pressed material (HIP) is required. To simulate the accelerated forming process, hot compression tests were performed with a DIL805A/D/T dilatometer from TA Instruments (New Castle, Delaware, USA) with different strain rates (0.0013, 0.005, 0.01 and 0.05) and temperatures (T=1150, 1175 and 1200°C). Deformation of the heat-treated state revealed lower flow stress (in both, peak stresses and steady state stresses) and fewer voids compared to the HIP state (Fig. 1.a). The compression test data were used to develop material and temperature specific strain rate profiles based on a material model. Subsequently, hot compression tests were performed with different strain rate profiles (starting strain rates 0.0013 and 0.0052) for the HIP and the HT state. The results were evaluated with regard to their microstructure, deformation, and damage behavior. A reduction of the processing time for all tested strain rates profiles by factors 2-3 could be achieved compared to constant strain rates. Furthermore, the results indicated that the deformation with strain rate profiles (compared to constant strain rates) did not significantly change the resulting microstructure or damage tolerance of the HT state.}, language = {en} } @misc{MorozovaObrosovNaumovetal., author = {Morozova, Iuliia and Obrosov, Aleksei and Naumov, Anton and Kr{\´o}licka, Aleksandra and Golubev, Iurii and Bokov, Dmitry O. and Doynov, Nikolay and Weiß, Sabine and Michailov, Vesselin}, title = {Impact of Impulses on Microstructural Evolution and Mechanical Performance of Al-Mg-Si Alloy Joined by Impulse Friction Stir Welding}, series = {Materials}, volume = {14}, journal = {Materials}, number = {2}, issn = {1996-1944}, doi = {https://doi.org/10.3390/ma14020347}, abstract = {Impulse Friction Stir Welding (IFSW) was utilized to join 6082-T6 alloy plates at various impulse frequencies. A distinctive feature of IFSW is the generation of mechanical impulses that enhances the forging action of the tool, and thereby, alters the weld microstructure. The microstructural evolution in the Stir Zone (SZ) with special focus on the strengthening precipitation behavior, and overall mechanical properties of the IFSW joints have been investigated. It was demonstrated that the strengthening β″ precipitates reprecipitated in the SZ of the IFSW joints during natural aging. In contrast, no precipitates were found in the SZ of the Friction Stir Welding (FSW) weld. Partial reversion of β″ after IFSW is supposed to occur due to more developed subgrain network and higher dislocation density introduced by impulses that accelerated precipitation kinetics. Dynamic recrystallisation was facilitated by impulses resulting in a fine, homogeneous structure. There was no significant difference between the microhardness in the SZ, tensile and yield strength of the FSW and IFSW joints. However, the application of impulses demonstrated the smoothing of the hardness reduction in the transition region at the advancing side. The shift of the fracture location from the Heat-Affected Zone (HAZ) by FSW to the SZ as well as higher elongation of the joints by IFSW of lower frequencies could be related to the grain refinement and the change of the grain orientation.}, language = {en} } @misc{BiedunkiewiczFigielGarbiecetal., author = {Biedunkiewicz, Anna and Figiel, Paweł and Garbiec, Dariusz and Obrosov, Aleksei and Pawlyta, Mirosława and Biedunkiewicz, Witold and Pruss, Przemysław and Rokosz, Krzysztof and Wr{\´o}bel, Rafał and Raaen, Steinar and Weiß, Sabine and Bokov, Dmitry O.}, title = {Influence of Elemental Carbon (EC) Coating Covering nc-(Ti,Mo)C Particles on the Microstructure and Properties of Titanium Matrix Composites Prepared by Reactive Spark Plasma Sintering}, series = {Materials}, volume = {14}, journal = {Materials}, number = {1}, issn = {1996-1944}, doi = {https://doi.org/10.3390/ma14010231}, abstract = {This paper describes the microstructure and properties of titanium-based composites obtained as a result of a reactive spark plasma sintering of a mixture of titanium and nanostructured (Ti,Mo)C-type carbide in a carbon shell. Composites with different ceramic addition mass percentage (10 and 20 wt \%) were produced. Effect of content of elemental carbon covering nc-(Ti,Mo)C reinforcing phase particles on the microstructure, mechanical, tribological, and corrosion properties of the titanium-based composites was investigated. The microstructural evolution, mechanical properties, and tribological behavior of the Ti + (Ti,Mo)C/C composites were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), electron backscatter diffraction analysis (EBSD), X-ray photoelectron spectroscopy (XPS), 3D confocal laser scanning microscopy, nanoindentation, and ball-on-disk wear test. Moreover, corrosion resistance in a 3.5 wt \% NaCl solution at RT were also investigated. It was found that the carbon content affected the tested properties. With the increase of carbon content from ca. 3 to 40 wt \% in the (Ti,Mo)C/C reinforcing phase, an increase in the Young's modulus, hardness, and fracture toughness of spark plasma sintered composites was observed. The results of abrasive and corrosive resistance tests were presented and compared with experimental data obtained for cp-Ti and Ti-6Al-4V alloy without the reinforcing phase. Moreover, it was found that an increase in the percentage of carbon increased the resistance to abrasive wear and to electrochemical corrosion of composites, measured by the relatively lower values of the friction coefficient and volume of wear and higher values of resistance polarization. This resistance results from the fact that a stable of TiO2 layer doped with MoO3 is formed on the surface of the composites. The results of experimental studies on the composites were compared with those obtained for cp-Ti and Ti-6Al-4V alloy without the reinforcing phase.}, language = {en} } @misc{StendalEisentrautSizovaetal., author = {Stendal, Johan Andreas and Eisentraut, Mark and Sizova, Irina and Bolz, Sebastian and Weiß, Sabine and Bambach, Markus}, title = {Accelerated hot deformation and heat treatment of the TiAl alloy TNM-B1 for enhanced hot workability and controlled damage}, series = {Journal of Materials Processing Technology}, volume = {Vol. 291}, journal = {Journal of Materials Processing Technology}, issn = {0924-0136}, doi = {10.1016/j.jmatprotec.2020.116999}, pages = {12}, language = {en} } @misc{FouziaFellahHeziletal., author = {Fouzia, Hammadi and Fellah, Mamoun and Hezil, Naouel and Aissani, Linda and Mimanne, Goussem and Mechachti, Said and Samad, Mohammed Abdul and Montagne, Alex and Iost, Alain and Weiß, Sabine and Obrosov, Aleksei}, title = {The effect of milling time on the microstructure and mechanical properties of Ti-6Al-4Fe alloys}, series = {Materials Today Communications}, volume = {27}, journal = {Materials Today Communications}, issn = {2352-4928}, doi = {10.1016/j.mtcomm.2021.102428}, pages = {11}, abstract = {Replacement of toxic and expensive vanadium (V) in medical grade titanium alloys with cheaper and non-toxic elements such as iron (Fe) or niobium (Nb), is an important step forward in developing safer and less expensive biomaterials. Evaluating the effect of different process parameters such as the milling time on the properties of these newly developed alloys helps in understanding and controlling their behavior. Hence, in this study, the influence of ball-milling duration (2, 6, 8, 12 and 18 h) on crystalline structure, phase evolution, densification, and mechanical characteristics of biomedical nanocrystalline Ti-6Al-4Fe (wt. \%) alloys is investigated. X-ray diffraction (XRD) confirmed that after 6 h of milling, aluminum (Al) and Fe completely dissolved into Ti matrix to form a solid solution of Ti (Al, Fe). XRD further revealed that the crystallite size decreased from 56 to 30 nm and the micro-strain increased with an increase in milling time. A decrease in porosity along with an increase in density is also observed for the alloys with increasing milling time. Moreover, the values of porosity obtained for the developed Ti-6Al-4Fe alloys ranged from 1 to 12 \%, which is comparable to the porosity of one of the cortical bones making it a potential candidate for bone replacements. Microhardness measurements showed that the hardness of the Ti-6Al-4Fe alloys was greater than the hardness of the conventional Ti-6Al-4V alloys. It was observed that the Ti-6Al-4Fe alloy fabricated with the powders milled for 2 h showed the lowest value of Young's Modulus. Milling time also had a significant effect on the surface roughness of the alloy samples, which showed a decreasing trend with increasing milling times.}, language = {en} } @misc{GrudininSidelevBleykheretal., author = {Grudinin, V. A. and Sidelev, D. V. and Bleykher, G. A. and Yuriev, Yu N. and Krivobokov, V. P. and Berlin, E. V. and Grigoriev, V. Yu and Obrosov, Aleksei and Weiß, Sabine}, title = {Hot target magnetron sputtering enhanced by RF-ICP source for CrNx coatings deposition}, series = {Vacuum}, volume = {191}, journal = {Vacuum}, issn = {0042-207X}, doi = {10.1016/j.vacuum.2021.110400}, pages = {9}, abstract = {This article describes hot Cr target magnetron sputtering enhanced by a radio-frequency inductively coupled plasma (RF-ICP) source in an Ar + N2 atmosphere. Optical emission spectroscopy revealed an opportunity to perform magnetron sputtering in an inert (Ar) atmosphere, while the CrNx coating can be deposited on a substrate in a chemically reactive atmosphere formed by the RF-ICP source. High stability and repeatability of deposition process were observed, and the deposition rate of the CrNx coatings increased from 106 to 127 nm/min as N2 flow rate rose. The power of the RF-ICP source and the N2 flow rate can be used to tailor and control deposition conditions. The XRD and WDS measurements showed the effect of deposition conditions on the crystal structure and elemental composition of CrNx coatings. It was found that the change of substrate bias, RF-ICP source power and N2 flow rate result in variation of coating stoichiometry from pure Cr to CrN.}, language = {en} } @misc{KrzywińskiSadowskiStefaniuketal., author = {Krzywiński, Kamil and Sadowski, Łukasz and Stefaniuk, Damian and Obrosov, Aleksei and Weiß, Sabine}, title = {Engineering and Manufacturing Technology of Green Epoxy Resin Coatings Modified with Recycled Fine Aggregates}, series = {International Journal of Precision Engineering and Manufacturing-Green Technology}, volume = {9}, journal = {International Journal of Precision Engineering and Manufacturing-Green Technology}, number = {1}, issn = {2198-0810}, doi = {10.1007/s40684-021-00377-w}, pages = {253 -- 271}, abstract = {Nowadays, the recycled fine aggregate sourced from construction and demolition waste is not frequently used in manufacturing of epoxy resin coatings. Therefore, the main novelty of the article is to prepare green epoxy resin coatings modified with recycled fine aggregate in a replacement ratio of natural fine aggregate ranged from 20 to 100\%. The microstructural properties of the aggregates and epoxy resin were analyzed using micro-computed tomography, scanning electron microscopy and nanoindentation. The macroscopic mechanical properties were examined using pull-off strength tests. The highest improvement of the mechanical properties was observed for epoxy resin coatings modified with 20\% of natural fine aggregate and 80\% of recycled fine aggregate. It has been found that even 100\% of natural fine aggregate can be successfully replaced using the recycled fine aggregate with consequent improvement of the pull-off strength of analyzed epoxy resin coatings. In order to confirm the assumptions resulting from the conducted research, an original analytical and numerical failure model proved the superior behavior of modified coating was developed.}, language = {en} } @misc{AissaniFellahChadlietal., author = {Aissani, Linda and Fellah, Mamoun and Chadli, Abdel Hakim and Samad, Mohammed Abdul and Cheriet, Abderrahmane and Salhi, Faiza and Nouveau, Corinne and Weiß, Sabine and Obrosov, Aleksei and Alhussein, Akram}, title = {Investigating the effect of nitrogen on the structural and tribo-mechanical behavior of vanadium nitride thin films deposited using R.F. magnetron sputtering}, series = {Journal of Materials Science}, volume = {56}, journal = {Journal of Materials Science}, number = {30}, issn = {1573-4803}, doi = {10.1007/s10853-021-06393-0}, pages = {17319 -- 17336}, abstract = {Magnetron sputtering is one of the most commonly used deposition techniques, which has received considerable attention in industrial applications. In particular, owing to its compatibility with conventional fabrication processes, it can produce and fabricate high-quality dense thin films of a wide range of materials. In the present study, nitrogen (N) was combined with pure vanadium in order to form binary nitride to improve its mechanical and tribological performance. To evaluate the influence of nitrogen on the structure of the as-deposited vanadium nitride (VN) coatings, the following techniques were used: XPS, XRD, SEM, AFM and optical profilometry. The residual stresses were determined by the curvature method using Stoney's formula. The hardness and Young's modulus were obtained by nanoindentation measurements. The friction behavior and wear characteristics of the films were evaluated by using a ball-on-disk tribometer. The obtained results showed that the N/V ratio increased with increasing the N2 flow rate while the deposition rate decreased. The preferred orientation was changed from (200) to (111) as the N2 flow rate increased with the presence of V-N and V-O binding energies as confirmed by XPS analysis. The nitrogen addition resulted in a columnar morphology and a fine structure with fine surface roughness. The VN thin film containing 49.5 at.\% of nitrogen showed the best performance: highest mechanical properties (hardness = 25 GPa), lowest friction coefficient (μ = 0.37) and lowest wear rate (Ws = 2.72 × 10-5 mm3N-1 m-1). A good correlation between the film microstructure, crystallite size, residual stress and mechanical and tribological properties was observed.}, language = {en} } @misc{ShapovalovShapovalovaOssenbrinketal., author = {Shapovalov, Oleg and Shapovalova, Mariia and Ossenbrink, Ralf and Heckel, Thomas and Michailov, Vesselin and Weiß, Sabine and Gaal, Mate}, title = {Verbessern der Korrosionsbest{\"a}ndigkeit eines hochtemperaturbest{\"a}ndigen Ultraschalld{\"a}mpfungsk{\"o}rpers mittels Laserstrahl-Auftragschweißen}, series = {DVS Berichte 2021}, journal = {DVS Berichte 2021}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-147-1}, pages = {370 -- 377}, abstract = {W{\"a}hrend in einem konventionellen Ultraschallpr{\"u}fkopf ein Kunststoffd{\"a}mpfungsk{\"o}rper mit Kleber oder {\"O}l an einen Piezoschwinger angekoppelt ist, werden als Hochtemperaturl{\"o}sung feinpor{\"o}se sintermetallische D{\"a}mpfungsmaterialien mit einer Fl{\"u}ssigglasankopplung eingesetzt. Um dabei das Sintermetall vor dem korrosiven Angriff der Glasschmelze zu sch{\"u}tzten, wird am D{\"a}mpfungsk{\"o}rper gegenw{\"a}rtig Gold- oder Platinfolie zeit- und kostenaufwendig appliziert. In der aktuellen Arbeit wurde eine Methode zum Korrosionsschutz der sintermetallischen Oberfl{\"a}che aus rostfreiem Stahl mittels Laser-Pulverauftragschweißen entwickelt. Im Laufe einer Schweißparameterstudie auf dem Substratmaterial aus massivem rostfreiem Stahl wurde die Eignung unterschiedlicher Auftragsmaterialien auf Nickel- und Kobaltbasis untersucht. Dabei wurde zun{\"a}chst der Einfluss verschiedener Schweißparameter wie Laserleistung, Vorschubgeschwindigkeit und Pulvermenge auf die Auftragsqualit{\"a}t (Nahtform, Vermischungsgrad, Porosit{\"a}t) metallografisch bewertet. Anschließend wurden die aufgetragenen Schichten hinsichtlich ihrer Korrosionsbest{\"a}ndigkeit getestet. Der Kontakt mit einer fl{\"u}ssigen Glasmischung bei 500 °C hat bei keiner der beschichteten Proben sichtbare Korrosionswirkung gezeigt. Als Resultat der Schweißparameterstudie haben sich besonders die nickelbasierten Pulver als gut geeignete Materialien f{\"u}r den Prozess gezeigt. Die identifizierten Schweißparameter wurden im n{\"a}chsten Schritt erfolgreich an das sintermetallische Substrat angepasst.}, language = {de} } @misc{ErmilovaNikitinWeiss, author = {Ermilova, Evgeniia and Nikitin, Alexander and Weiß, Sabine}, title = {The Local Strain Evolution for Structured Sheet Metals During Uniaxial Deformation}, series = {Forming the Future : Proceedings of the 13th International Conference on the Technology of Plasticity}, journal = {Forming the Future : Proceedings of the 13th International Conference on the Technology of Plasticity}, editor = {Daehn, Glenn and Cao, Jian and Kinsey, Brad and Tekkaya, A. Erman and Vivek, Anupam and Yoshida, Yoshinori}, edition = {1}, publisher = {Springer, Cham}, isbn = {978-3-030-75381-8}, issn = {2367-1696}, doi = {10.1007/978-3-030-75381-8_143}, pages = {1701 -- 1711}, abstract = {Structured materials can be progressive alternatives to commonly used flat sheets because of their higher bending stiffness and stability compared to flat sheet metals, made of the same alloy. The application of sheet metals requires accurate information regarding their strength and deformation behavior. Such data are not commonly available and have to be measured by specific test setups and implementation of tests. The aim of this work is to obtain new knowledge about deformation mechanisms of structured sheet metals. Structured sheet metals (SSM) made of conventional deep-drawing steel DC04 were investigated by means of tensile tests. The influence of the structure type arrangement on the deformation behavior was analyzed. The evolution of local strains was analyzed by means of strain gauge measurements as well as 3D-displacement measurements with an ARAMIS highresolution camera system. Local orientation changes in different structural elements were measured using the electron backscatter diffraction technique.}, language = {en} } @misc{EmdadiBolzBuhletal., author = {Emdadi, Aliakbar and Bolz, Sebastian and Buhl, Johannes and Weiß, Sabine and Bambach, Markus}, title = {Laser Powder Bed Fusion Additive Manufacturing of Fe3Al-1.5Ta Iron Aluminide with Strengthening Laves Phase}, series = {Metals}, volume = {12}, journal = {Metals}, number = {6}, issn = {2075-4701}, doi = {10.3390/met12060997}, language = {en} } @misc{ShapovalovHeckelGaaletal., author = {Shapovalov, Oleg and Heckel, Thomas and Gaal, Mate and Weiß, Sabine}, title = {External Acoustical Damping on a Metallic Angle Wedge in a High Temperature Resistant Ultrasonic Probe}, series = {Acoustics Australia}, volume = {50}, journal = {Acoustics Australia}, number = {3}, issn = {1839-2571}, doi = {10.1007/s40857-022-00270-9}, pages = {343 -- 353}, abstract = {Ultrasonic probes for high-temperature applications are provided with metallic wedges, which can withstand the contact with the high temperature of the inspected structure. The ultrasonic signal travels within the wedge and gets reflected from its boundaries, causing interference signals called "ghost echoes". The current work presents an investigation of the additional damping effect provided by porous sintered metal plates applied onto the surface of the wedge. In particular, the study evaluates the effect of damping plate thickness on the interference signal level at different transmission frequencies. Damping plates made of sintered metal SIKA-R 15 AX were attached to a wedge prototype made of steel 1.4301. The study revealed, that the most effective thickness of damping plates in the selected frequency interval of 1 to 4 MHz is equal to 4 mm. The evaluation of the interference signal has shown that the application of such damping plates to the wedge surface contributes to an additional attenuation of an interference signal of 10 to 30 dB after 500 µs of signal propagation.}, language = {en} } @misc{MorozovaKehmObrosovetal., author = {Morozova, Iuliia and Kehm, Christian and Obrosov, Aleksei and Yang, Yitong and Miah, Kamal Uddin Mohammad and Uludintceva, Elena and Fritzsche, Sebastian and Weiß, Sabine and Michailov, Vesselin}, title = {On the Heat Treatment of Selective-Laser-Melted 316L}, series = {Journal of Materials Engineering and Performance}, volume = {32 (2023)}, journal = {Journal of Materials Engineering and Performance}, number = {10}, issn = {1544-1024}, doi = {10.1007/s11665-022-07404-0}, pages = {4295 -- 4305}, abstract = {The effect of heat treatment at various temperatures (650, 850, 1050, and 1100°C) and dwell times (10 min and 1 h) on the metallurgical and microstructural evolution as well as on the related tensile properties of stainless steel 316L processed by selective laser melting (SLM) has been systematically evaluated. The metallurgical and microstructural features such as defects, stability of the columnar-cellular structure and substructure, second phase particles, and phase transformation imparted by SLM and heat treatment have been discussed. It has been shown that the processing conditions specific to SLM significantly alter the kinetics of phase evolution compared to standard welding techniques which affects the accuracy of the prediction. The influence of these characteristics on tensile properties and hardness was elucidated. It was disclosed that with increasing heat treatment temperature there was a gradual increase in elongation but a decrease in strength related to the dislocation density and the development of the microstructure.}, language = {en} } @misc{MorozovaKrolickaObrosovetal., author = {Morozova, Iuliia and Kr{\´o}licka, Aleksandra and Obrosov, Aleksei and Yang, Yitong and Doynov, Nikolay and Weiß, Sabine and Michailov, Vesselin}, title = {Precipitation phenomena in impulse friction stir welded 2024 aluminium alloy}, series = {Materials Science and Engineering: A}, journal = {Materials Science and Engineering: A}, issn = {0921-5093}, doi = {10.1016/j.msea.2022.143617}, pages = {1 -- 11}, abstract = {Microhardness variations across the friction stir welded (FSW) and impulse friction stir welded (IFSW) AA2024-T351 joints have been elucidated by the transformations of the S-Al2CuMg phase with a special focus on a distinguished hardness peak within the heat-affected zone (HAZ) of the impulse welds. The increase in hardness within the stir zone (SZ) originated from the partial re-precipitation of the initial Guinier-Preston-Bagaryatsky zones (GPB) and metastable S needles, previously dissolved.) Formation and growth of stable S precipitates via coalescence accounted for the softening through the thermo-mechanically affected zone (TMAZ). The peak strengthening within the HAZ of the IFSW joints was mainly caused by the dense needle-shaped S particles, which can be explained by a mutual influence of the process specific temperature and strain cycles. Dislocations and subgrain boundaries introduced to the material due to plastic deformation facilitated the nucleation of strengthening S precipitates in the HAZ. It demonstrates that the impact of deformation should be considered by the characterization of the precipitation development in the HAZ.}, language = {en} } @misc{FigielBiedunkiewiczJachetal., author = {Figiel, Paweł and Biedunkiewicz, Anna and Jach, Katarzyna and Obrosov, Aleksei and Garbiec, Dariusz and Bik, Maciej and Sitarz, Maciej and Kucia, Zofia and Pawlyta, Mirosława and Weiß, Sabine}, title = {Ti-Mo-xTiC composites manufactured by U-FAST reactive sintering}, series = {International Journal of Refractory Metals and Hard Materials}, journal = {International Journal of Refractory Metals and Hard Materials}, number = {108}, issn = {0263-4368}, doi = {10.1016/j.ijrmhm.2022.105960}, pages = {1 -- 14}, abstract = {The paper presents the characteristics of Ti-Mo-xTiC composites manufactured under experimentally selected conditions using the upgraded field-assisted sintering technique (U-FAST). Mixtures of microstructural titanium powders and nc-Ti0.9Mo0.1C/C carbide powders protected from oxidation by a carbon shell were subjected to sintering. The powders with nc-Ti0.9Mo0.1C/C contents of 10 and 20 wt\% were used. The content of carbon forming the carbon shell was approximately 3 or 40 wt\%. Composites with near full density were reinforced with titanium carbides in a Ti-Mo matrix. The composites with the highest content of reinforcing phase are characterized by the highest values of hardness, Young's modulus and wear resistance. Although the hardness of these composites is similar to that of ceramics, their nature is not brittle. Despite the high value of the Young's modulus, the addition of hard particles of the reinforcing phase to the titanium matrix significantly increases the values of the H/E ratio of the composites compared to the reference samples of cp-Ti and Ti6Al4V. A comparison of the research results for the composites with the highest share of titanium carbides showed that lowering the sintering temperature from 1300 to 1150 °C resulted in the inhibition of grain growth, a reduction in composite heterogeneity, composite roughness and hardness as well as a rise in the Young's modulus. An increase in the sintering temperature from 1150 to 1300 °C contributed to the higher high angle grain boundaries (HAGB) content.}, language = {en} } @misc{PetkovBakalovaObrosovetal., author = {Petkov, Nikolay and Bakalova, Totka and Obrosov, Aleksei and Kashkarov, Egor B. and Kormunda, Martin and Kejzlar, Pavel and Bahchedzhiev, Hristo and Dadourek, Karel and Weiß, Sabine}, title = {Structural, mechanical, and tribological properties of CrCN coatings obtained by cathodic arc physical vapour deposition technology at different CH4/N2 gas ratio}, series = {Thin Solid Films}, volume = {766}, journal = {Thin Solid Films}, issn = {1879-2731}, doi = {10.1016/j.tsf.2022.139669}, abstract = {Chromium carbonitride coatings were deposited by cathodic arc physical vapor deposition technology at a temperature of 300 °C, as were used the reactive gasses CH4 and N2. The structural analysis of the CrN coating showed a polycrystalline structure with mixed CrN and Cr2N phases. All studied coatings, including the CrC exhibits fcc structure. The phases were confirmed by X-ray photoelectron spectroscopy measurements where a surface oxidation was also detected. The increase of the CH4 gas flow during the deposition process leads to a parabolic trend with the highest hardness of 33.5 GPa for the coating deposited at CH4 / N2 = 0.53. At the same time the lowest coefficient of friction for both counterparts Al2O3 and ZrO2 (0.28 and 0.26, respectively) were measured at CH4 / N2 = 1.86. The tribological tests reveal that the wear of the coatings increases with an increasing CH4 flow rate, whereas the coefficient of friction decreases. This observed contradiction is explained by a phenomenon described as the effect of Rebinder.}, language = {en} } @misc{GrudininBleykherKrivobokovetal., author = {Grudinin, V. A. and Bleykher, G. A. and Krivobokov, V. P. and Semyonov, O. V. and Obrosov, Aleksei and Weiß, Sabine and Sidelev, D. V.}, title = {Hot target magnetron sputtering enhanced by RF-ICP source: Microstructure and functional properties of CrNx coatings}, series = {Vacuum}, volume = {200}, journal = {Vacuum}, issn = {1879-2715}, doi = {10.1016/j.vacuum.2022.111020}, abstract = {CrNx coatings were deposited at high rates (100-130 nm/min) using hot Cr target magnetron sputtering enhanced by a radio-frequency inductively coupled plasma (RF-ICP) source in an Ar + N2 atmosphere. Besides separation of inert and reactive atmosphere, the RF-ICP source can be an effective tool for ion assistance in case of coating growth and to tailor film parameters. The effects of nitrogen flow rate and substrate bias potential on microstructure and functional properties of the CrNx coatings were investigated. An increase in nitrogen flow rate favored the formation of a looser microstructure of the coatings, while substrate biasing had the opposite effect. The functional properties were strongly dependent on the phase composition of the CrNx coatings. The change in coating microstructure significantly affected hardness, elastic modulus, adhesion, friction coefficients and corrosion resistance. The results indicated that ion assistance can be a key feature for regulating functional properties in the considered type of coating deposition. Cr2N and CrN compound coatings with high hardness (∼20 GPa) and low corrosion current density (icorr ∼ 3-5·10-9 A/cm2) in a 3.5 wt\% NaCl solution were obtained by high-rate deposition.}, language = {en} } @misc{AlontsevaSafarovaYantsenVoinarovychetal., author = {Alontseva, Darya and Safarova (Yantsen), Yuliya and Voinarovych, Sergii and Obrosov, Aleksei and Yamanoglu, Ridvan and Khoshnaw, Fuad and Yavuz, Hasan Ismail and Nessipbekova, Assem and Syzdykova, Aizhan and Azamatov, Bagdat and Khozhanov, Alexandr and Weiß, Sabine}, title = {Biocompatibility and Corrosion of Microplasma-Sprayed Titanium and Tantalum Coatings versus Titanium Alloy}, series = {Coatings}, volume = {14}, journal = {Coatings}, number = {2}, issn = {2079-6412}, doi = {10.3390/coatings14020206}, abstract = {This study investigates the in vitro biocompatibility, corrosion resistance, and adhesion strength of a gas abrasive-treated Ti6Al4V alloy, alongside microplasma-sprayed titanium and tantalum coatings. Employing a novel approach in selecting microplasma spray parameters, this study successfully engineers coatings with tailored porosity, roughness, and over 20\% porosity with pore sizes up to 200 μm, aiming to enhance bone in-growth and implant integration. This study introduces an innovative methodology for quantifying surface roughness using laser electron microscopy and scanning electron microscopy, facilitating detailed morphological analysis of both the substrate and coatings. Extensive evaluations, including tests for in vitro biocompatibility, corrosion resistance, and adhesive strength, revealed that all three materials are biocompatible, with tantalum coatings exhibiting superior cell proliferation and osteogenic differentiation, as well as the highest corrosion resistance. Titanium coatings followed closely, demonstrating favorable osteogenic properties and enhanced roughness, which is crucial for cell behavior and attachment. These coatings also displayed superior tensile adhesive strengths (27.6 ± 0.9 MPa for Ti and 28.0 ± 4.9 MPa for Ta), surpassing the ISO 13179-1 standard and indicating a robust bond with the substrate. Our findings offer significant advancements in biomaterials for medical implants, introducing microplasma spraying as a versatile tool for customizing implant coatings, particularly emphasizing the superior performance of tantalum coatings in terms of biocompatibility, osteogenic potential, and corrosion resistance. This suggests that tantalum coatings are a promising alternative for enhancing the performance of metal implants, especially in applications demanding high biocompatibility and corrosion resistance.}, language = {en} } @misc{FellahHezilBourasetal., author = {Fellah, Mamoun and Hezil, Naouel and Bouras, Dikra and Bouchareb, Nabila and Larios, Alejandro Perez and Obrosov, Aleksei and El-Hiti, Gamal A. and Weiß, Sabine}, title = {Investigating the effect of Zr content on electrochemical and tribological properties of newly developed near β-type Ti-alloys (Ti-25Nb-xZr) for biomedical applications}, series = {Journal of Science: Advanced Materials and Devices}, journal = {Journal of Science: Advanced Materials and Devices}, issn = {2468-2179}, doi = {10.1016/j.jsamd.2024.100695}, abstract = {In order to create alloys with exceptional properties for orthopedic uses, this study focuses on the impact of zirconium (Zr) content on the structural, electrochemical, and tribological qualities of nanostructured Ti-25Nb-xZr [x = 5, 10, 15, 20, 25, and 30 atomic (at.) \%] alloys. The structural evolution was investigated using XRD and SEM techniques. The mechanical characteristics of the produced alloys, including Vickers hardness and Young's modulus, were measured. In addition, the corrosion tests were performed using the OCP, EIS, and PD methods in Ringer's solution within the independent pH range at 37 °C. A ball-on-disc tribometer was used to investigate the tribological behavior of the alloys under various loads and wet conditions using the Ringer solution. It has been verified that Zr content (at. \%) in the alloys had an impact on their morphologies, structural evolution, and mechanical characteristics. According to the morphological analysis, the particle and crystallite size decreases with increasing Zr content. Young's modulus and Vickers hardness show the same tendency. The EIS data demonstrated that a single passive film formed on the alloy surfaces, and the addition of Zr enhanced the corrosion resistance of the passive films. The polarization curves demonstrate that the alloys had low corrosion current densities and large passive areas without the passive films disintegrating. Likewise, the inclusion of Zr resulted in a reduction in the corrosion and passive current densities values. All of these results suggested that the titanium alloys exhibit a more noble electrochemical activity caused by Zr. From the tribological perspective, it was found that the friction coefficient of the alloys reduced with increasing Zr content.}, language = {en} } @misc{FellahBoucharebHeziletal., author = {Fellah, Mamoun and Bouchareb, Nabila and Hezil, Naouel and Merah, Ne{\c{c}}ar and Alashkar, Yasser and Imran, Mohd and Obrosov, Aleksei and Weiß, Sabine}, title = {Electrochemical analysis of mechanically alloyed Ti50\%-Ni50\% alloy for bone implants use}, series = {Journal of Alloys and Compounds}, journal = {Journal of Alloys and Compounds}, number = {1010}, issn = {1873-4669}, doi = {https://doi.org/10.1016/j.jallcom.2024.178046}, pages = {1 -- 13}, abstract = {The corrosion resistance of an implant material is an essential element of its biocompatibility. This research focuses on studying the effect of grinding/milling time on the corrosion behavior of the mechanically alloyed Ti50 \%-Ni50 \% (at\%) alloy, for bone implant use, at varying milling times of 2, 6, 12, and 18 h. The powder particles' size, shape, and homogeneous chemical content were examined employing scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The alloyed particles' structural characteristics were determined by X-ray diffraction (XRD). Moreover, the characterization of the electrochemical properties was performed utilizing open-circuit potential (OCP) measurement, the Potentiodynamic Polarization (PD), and the Electrochemical Impedance Spectroscopy (EIS) technique. Electrochemical tests were conducted in physiological mediums simulating the human body: Hank's solution. The results revealed that; as the grinding time increased the crystallite size reduced from 57 nm to 29 nm, whereas the lattice parameters increased slightly from 3.18 to 3.22 {\AA}, while the microstrain increased from 0.32 \% to 0.99 \%. Moreover, the hardness and Young's Modulus increased by about 70 and 16 \%, respectively with milling period going from 2 to 18 h. The findings of the electrochemical test demonstrated that as milling progressed, corrosion resistance increased. The evolution of OCP curves as a function of the duration of immersions indicated that OCP increased with the duration of immersion up to 2500 s; this is due to a stable passive layer that has formed on the samples' surface. The results of potentiodynamic polarization curves revealed that both corrosion current density (icorr) and corrosion rate (CR) decreased reaching a value of 3.6945E-07 A/cm2 and 0.0074722 mm/year, respectively, at longer milling time (18 h). While, corrosion potential (Ecorr) increased from -0.51255 V/SCE to -0.29997 V/SCE with increasing grinding time. Additionally, the EIS data indicated that the resistance of the passive film increased with increasing milling times. The samples of Ti50-Ni50 produced at longer milling time exhibited excellent corrosion resistance due to the formation of a stable passive film which makes them useful for bone implants.}, language = {en} } @misc{AlontsevaSafarovaYantsenVoinarovychetal., author = {Alontseva, Darya and Safarova (Yantsen), Yuliya and Voinarovych, Sergii and Obrosov, Aleksei and Yamanoglu, Ridvan and Khoshnaw, Fuad and Nessipbekova, Assem and Syzdykova, Aizhan and Yavuz, Hasan Ismail and Kaliuzhnyi, Sergii and Krasavin, Alexander and Azamatov, Bagdat and Khozhanov, Alexandr and Olzhayev, Farkhad and Weiß, Sabine}, title = {Microplasma-Sprayed Titanium and Hydroxyapatite Coatings on Ti6Al4V Alloy: in vitro Biocompatibility and Corrosion Resistance: Part I}, series = {Johnson Matthey Technology Review}, volume = {69}, journal = {Johnson Matthey Technology Review}, number = {1}, doi = {10.1595/205651325X17201903387613}, pages = {45 -- 58}, abstract = {This two-part paper investigates the bioactivity and mechanical properties of coatings applied to Ti6Al4V, a common titanium alloy used in endoprosthetic implants. Coatings made from hydroxyapatite (HA) powder and commercially pure titanium (CP-Ti) wires were applied using microplasma spraying. The study focuses on the responses of rat mesenchymal stem cells (MSCs), which are essential for bone healing, to these coatings. Part I shows how adjusting the microplasma spraying process allows coatings with varying porosity and surface roughness to be achieved.}, language = {en} } @misc{AlontsevaSafarovaYantsenVoinarovychetal., author = {Alontseva, Darya and Safarova (Yantsen), Yuliya and Voinarovych, Sergii and Obrosov, Aleksei and Yamanoglu, Ridvan and Khoshnaw, Fuad and Nessipbekova, Assem and Syzdykova, Aizhan and Yavuz, Hasan Ismail and Kaliuzhnyi, Sergii and Krasavin, Alexander and Azamatov, Bagdat and Khozhanov, Alexandr and Olzhayev, Farkhad and Weiß, Sabine}, title = {Microplasma-sprayed titanium and hydroxyapatite coatings on Ti6Al4V alloy: in vitro biocompatibility and corrosion resistance : part II coatings enhance cell proliferation, corrosion resistance and implant integration}, series = {Johnson Matthey Technology Review}, volume = {69 (2025)}, journal = {Johnson Matthey Technology Review}, number = {1}, issn = {2056-5135}, doi = {10.1595/205651325X17290035905758}, pages = {59 -- 75}, abstract = {Part II presents the results which show that HA coatings significantly enhance MSC proliferation by 13\% compared to the titanium alloy base, while titanium coatings also exhibit an 11\% increase. Porosity inversely affects CP-Ti's elasticity. Coatings with lower porosity demonstrate better corrosion resistance. HA coatings promote osteogenic activity and angiogenesis, which is crucial for implant integration.}, language = {en} } @misc{SynodinosKarnatakAguilar‐Triguerosetal., author = {Synodinos, Alexis D. and Karnatak, Rajat and Aguilar-Trigueros, Carlos A. and Gras, Pierre and Heger, Tina and Ionescu, Danny and Maaß, Stefanie and Musseau, Camille L. and Onandia, Gabriela and Planillo, Aimara and Weiss, Lina and Wollrab, Sabine and Ryo, Masahiro}, title = {The rate of environmental change as an important driver across scales in ecology}, series = {Oikos}, volume = {2023}, journal = {Oikos}, number = {4}, publisher = {Wiley}, issn = {0030-1299}, doi = {10.1111/oik.09616}, pages = {11}, abstract = {Global change has been predominantly studied from the prism of 'how much' rather than 'how fast' change occurs. Associated to this, there has been a focus on environmental drivers crossing a critical value and causing so-called regime shifts. This presupposes that the rate at which environmental conditions change is slow enough to allow the ecological entity to remain close to a stable attractor (e.g. an equilibrium). However, environmental change is occurring at unprecedented rates. Equivalently to the classical regime shifts, theory shows that a critical threshold in rates of change can exist, which can cause rate-induced tipping (R-tipping). However, the potential implications of R-tipping in ecology remain understudied. We aim to facilitate the application of R-tipping theory in ecology with the objective of identifying which properties (e.g. level of organisation) increase susceptibility to rates of change. First, we clarify the fundamental difference between tipping caused by the magnitude as opposed to the rate of change crossing a threshold. Then we present examples of R-tipping from the ecological literature and seek the ecological properties related to higher sensitivity to rates of change. Specifically, we consider the role of the level of ecological organisation, spatial processes, eco-evolutionary dynamics and pair-wise interactions in mediating or buffering rate-induced transitions. Finally, we discuss how targeted experiments can investigate the mechanisms associated to increasing rates of change. Ultimately, we seek to highlight the need to better understand how rates of environmental change may induce ecological responses and to facilitate the systematic study of rates of environmental change in the context of current global change.}, language = {en} } @misc{YangWeiss, author = {Yang, Yitong and Weiß, Sabine}, title = {In-situ investigation on cyclic bending deformation of oligocrystalline 316LVM steel for coronary stent application with EBSD}, series = {International Conference on Strength of Materials 2022}, journal = {International Conference on Strength of Materials 2022}, publisher = {HAL open science}, pages = {9}, abstract = {The objective of this work is to investigate the strain localization and slip activation of the microstructure of oligo-crystalline 316LVM steel struts evolving during different cyclic bending deformation stages (number of cycles) and loading conditions (maximum stress and neutral). A micro-scale three-point bending fixture was designed and incorporated into a micro tensile/compression machine inside a scanning electron microscope (SEM) to perform in-situ electron backscatter diffraction (EBSD) measurements during different phases of cyclic fatigue testing. The following results were obtained: 1) The quantitative strain could be compared after each stage of deformation. 2) The rotation of the grains orientations is observed during the cyclic deformation while the morphology did not change significantly. The results contribute to the understanding of the evolution of the microstructure at low strain variations under bending fatigue conditions, and can support the prediction of the fatigue life of 316LVM stainless steel oligocrystalline microdevices like coronary artery stents.}, language = {en} } @misc{FellahHezilBourasetal., author = {Fellah, Mamoun and Hezil, Naouel and Bouras, Dikra and Obrosov, Aleksei and Samad, Mohammed Abdul and Montagne, Alex and Abd-Elmonem, Assmaa and Din, Sayed M El and Weiß, Sabine}, title = {Structural, mechanical and tribological performance of a nano structured biomaterial Co-Cr-Mo alloy synthesized via mechanical alloying}, series = {Journal of Materials Research and Technology}, volume = {25}, journal = {Journal of Materials Research and Technology}, issn = {2214-0697}, doi = {10.1016/j.jmrt.2023.06.031}, pages = {2152 -- 2165}, abstract = {The influence of milling time on the tribological behavior of a Co-Cr-Mo alloy designed for biomedical applications, synthesized via mechanical alloying is investigated. Elemental Co, Cr and Mo powders are milled using different milling times (2, 6, 12 and 18 h) in a high-energy ball mill. The resulting powders were subjected to cold uniaxial and hot isostatic pressing respectively, followed by sintering to obtain cylindrical samples, which were evaluated for their structural, mechanical and the wear behavior. Results showed that the grain and crystallite sizes of the powders decreased with increasing milling time, reaching low values of <10 μm and 32 μm respectively, at higher milling times. Furthermore, the wear rates and the coefficients of friction were lower, at higher milling times due to high densities (96\%), and higher elasto-plastic resistance, as presented by the H/E and H3/E2 values of 0.026 and 0.0021 GPa, respectively. Increased milling time enables the refinement of grains and reduction in porosity in the Co-Cr-Mo alloy, which in turn increases the alloy's elasto-plastic resistance and enhances its wear resistance.}, language = {en} } @misc{CelikAtapekPolatetal., author = {{\c{C}}elik, G{\"u}l{\c{s}}ah Akta{\c{s}} and Atapek, Şaban Hakan and Polat, Şeyda and Obrosov, Aleksei and Weiß, Sabine}, title = {Nitriding Effect on the Tribological Performance of CrN-, AlTiN-, and CrN/AlTiN-Coated DIN 1.2367 Hot Work Tool Steel}, series = {Materials}, volume = {16}, journal = {Materials}, number = {7}, issn = {1996-1944}, doi = {10.3390/ma16072804}, abstract = {In this study, heat-treated and multisurface engineered DIN 1.2367 tool steel was subjected to room and elevated temperature wear tests, and the effect of nitriding on its tribological behavior was investigated. CrN, AlTiN, and CrN/AlTiN coatings with a total thickness of 2 µm were obtained by arc cathodic physical vapor deposition on conventional heat-treated and gas-nitrided steels. The white layer formed during nitriding was removed, and a diffusion layer (100 µm) was achieved in the cross section of the steel having a tempered martensitic matrix. The highest surface hardness was attained with an integral coating (CrN/AlTiN), and surface hardness increased even more after nitriding due to the formation of a multicomponent ceramic layer on top of the diffusion layer. The room temperature wear tests performed against an alumina counterpart revealed that (i) CrN/AlTiN-coated steel had the highest friction coefficient of 0.26, which further increased to 0.33 by nitriding due to the increase in shear strength, and that (ii) with increasing surface hardness, the specific wear rates (W) of the heat-treated and coated steels could be ranked as follows: WCrN/AlTiN < WAlTiN < WCrN. The wear rates decreased when nitriding was carried out prior to coating. In order to simulate the aluminum extrusion conditions, hot wear behavior of the surfaces against AA6080 alloy at 450 °C was investigated. The hot wear tests revealed that (i) high friction coefficients were reached due to the adhesive characteristic of aluminum to the surfaces, (ii) the nitrided and CrN/AlTiN-coated sample exhibited the lowest wear rate among all studied surfaces, and (iii) the film damage on the worn surfaces mostly occurred in the form of droplet delamination.}, language = {en} } @misc{SafariImranWeiss, author = {Safari, Athar and Imran, Muhammad and Weiss, Sabine}, title = {A Comparative Study on Modified Johnson-Cook and Arrhenius-Type Constitutive Models to Predict the Hot Deformation Behaviour of Molybdenum-Hafnium-Carbide Alloy}, series = {Journal of Materials Engineering and Performance}, volume = {30}, journal = {Journal of Materials Engineering and Performance}, number = {3}, issn = {1059-9495}, doi = {10.1007/s11665-021-05464-2}, pages = {1945 -- 1956}, abstract = {Molybdenum alloys are commonly used as tool material for high-temperature deformation processes like forming or forging. For these types of application, the material has to withstand static load at elevated temperatures. To investigate the high-temperature performance of the material, uniaxial hot tensile tests were performed on a Mo-1.2\% Hf-0.1\% C alloy (MHC) over the temperature range of 1173-1473 K with intervals of 100 K and strain rates of 0.001, 0.01 and 0.1 s-1 up to the fracture of the specimen. The flow stress decreases with increase in temperature and the reduction in strain rate. This behaviour could be related to the increasing rate of restoration mechanisms, i.e. dynamic recrystallization or recovery as well as to the decrease in the strain hardening rate. Microstructure of the two most critical hot deformation conditions were shown and compared. Based on modified Johnson-Cook and strain-compensated Arrhenius-type models, constitutive equations were established to predict the high-temperature flow stress of the respective MHC alloy. The accuracy of both models was evaluated by comparing the predicted stress values and the values obtained from experiments. Correlation coefficient, average absolute relative error, the number of material constants involved and the computational time required for evaluating the constants were calculated to quantify and compare the precision of both models. The flow stress values predicted by the constitutive equations are in good agreement with the experimental results. At lower strain rates (0.001 and 0.01 s-1), distinct deviation from the experimental results can be observed for the modified Johnson-Cook model. Despite the longer evaluation time and the larger number of material constants, the deformation behaviour, tracked by the Arrhenius-type model is more accurate throughout the entire deformation process.}, language = {en} } @misc{BourasFellahBarilleetal., author = {Bouras, Dikra and Fellah, Mamoun and Barille, Regis and Weiß, Sabine and Samad, Mohammed Abdul and Alburaikan, Alhanouf and Khalifa, Hamiden Abd El-Wahed and Obrosov, Aleksei}, title = {Improvement of photocatalytic performance and sensitive ultraviolet photodetectors using AC-ZnO/ZC-Ag2O/AZ-CuO multilayers nanocomposite prepared by spin coating method}, series = {Journal of Science: Advanced Materials and Devices}, volume = {9}, journal = {Journal of Science: Advanced Materials and Devices}, number = {1}, issn = {2468-2179}, doi = {10.1016/j.jsamd.2023.100642}, abstract = {Morphological and optical properties of a multilayer film (CAZO/CZAO/ZACO) prepared by spin-coating method and deposited on a glass substrate were evaluated. The study was initially carried out for each layer, individually and then as a multilayer subsequently. Structural properties using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), infrared spectra (IR) and X-ray photoelectron Spectroscopy (XPS) showed the presence of three phases of zinc, copper and silver oxides at different levels. The CZAO sample observed with scanning electron microscope (SEM) showed an excellent porous surface with a large deformation in the multilayer configuration. Doping with zinc and copper in the silver crystal lattice improved the crystal structure and reduced the optical energy gap, thus increasing the optical absorbance and refractive index. The dielectric constants and showed an increase in the optical polarization values for lower photonic energies. The maximum degradation rate for photocatalysts of methylene blue was 89 \% for a 5-h exposure period with CAZO/CZAO/ZACO while it reached 71 \% for the CZAO sample during the same time period. The sensitivity of samples to light proved that the presence of ultraviolet radiation increases the number of holes trapped by oxygen ions and causes more free electrons and contribute to a better production of photocurrent than in darkness.}, language = {en} } @misc{YangEisentrautWeissetal., author = {Yang, Yitong and Eisentraut, Mark and Weiß, Sabine and Bolz, Sebastian}, title = {Comparison of the data from two EBSD system to verify the accuracy of the technique}, series = {AK Treffen Mikrostrukturcharakterisierung im REM", Ruhr-Uni Bochum, 30. November - 1. Dezember 2023}, journal = {AK Treffen Mikrostrukturcharakterisierung im REM", Ruhr-Uni Bochum, 30. November - 1. Dezember 2023}, address = {Bochum}, pages = {11}, language = {en} } @misc{EmdadiYangBolzetal., author = {Emdadi, Aliakbar and Yang, Yitong and Bolz, Sebastian and Stryzhyboroda, Oleg and Tovar, Michael and Gein, Sergej and Hecht, Ulrike and Weiß, Sabine}, title = {Mechanisms of necklace recrystallization in a BCC Fe-Al-Ta alloy with strengthening Laves phase precipitates}, series = {Scripta Materialia}, volume = {237}, journal = {Scripta Materialia}, issn = {1359-6462}, doi = {10.1016/j.scriptamat.2023.115705}, pages = {6}, abstract = {A necklace structure composed of fine grains formed by dynamic recrystallization was uncommonly observed at the pre-existing grain boundaries during the hot compression of a BCC Fe-25Al-1.5Ta alloy containing C14 - (Fe, Al)2Ta Laves phase precipitates. Two possible mechanisms for necklace formation were proposed; particle-stimulated nucleation and grain boundary bulging, depending on whether the original grain boundaries are occupied by C14 particles, or they are free of them. Recrystallization was initiated preferentially around the clusters of large particles at the boundaries containing particles. In contrast, the bulging of the original grain boundaries by strain-induced boundary migration was observed as a preliminary stage for necklace formation at the particle-free boundaries. The necklace structure expanded into the deformed volume in such a way that low-angle subgrain boundaries decorating the necklace layers transformed into grains with increasing deformation strain.}, language = {en} } @misc{LaskoYangWeissetal., author = {Lasko, Galina and Yang, Yitong and Weiss, Sabine and Schmauder, Siegfried and Dogahe, Kiarash}, title = {FEM Simulations of Fatigue Crack Initiation in the Oligocrystalline Microstructure of Stents}, series = {Materials}, volume = {16}, journal = {Materials}, number = {17}, doi = {10.3390/ma16176003}, pages = {17}, abstract = {For over two decades, vascular stents have been widely used to treat clogged vessels,serving as a scaffold to enlarge the narrowed lumen and recover the arterial flow area. High-purityoligocrystalline austenitic steel is usually applied for the production of stents. Despite the popularityand benefit of stenting, it still may cause serious clinical adverse issues, such as in-stent restenosisand stent fracture. Therefore, the study of the mechanical properties of stents and in particularthe prediction of their life cycles are in the focus of materials research. In our contribution, withinthe finite element method, a two-scale model of crack initiation in the microstructure of stents iselaborated. The approach is developed on the basis of the physically based Tanaka-Mura model(TMM), considering the evolution of shear bands during the crack initiation phase. The model allowsfor the analysis of the microstructure with respect to the life cycles of real materials. The effects ofdifferent loading conditions, grain orientation, and thickness of the specimen on W{\"o}hler curves wereanalysed. It was found that the microstructural features of oligocrystals are very sensitive to differentloading conditions with respect to their fatigue behaviour and play a major role in fatigue crackinitiation. Different grain-orientation distributions result in qualitative and quantitative differencesin stress distribution and in the number of cycles for crack initiation. It was found that presence ofa neutral zone in the cut-out of the microstructure under three-point-bending loading conditionschanges the qualitative and quantitative patterns of stress distribution and affects the number ofcycles for crack initiation. It was found that under both tensile and bending loading conditions,thicker specimens require more cycles for crack initiation. The W{\"o}hler curves for crack initiation inoligocrystalline microstructures of stents could be compared with the ones in the experiment, takinginto account that for high cyclic fatigue (HCF), typically, more than 70\% of the cycles refer to crackinitiation. The developed numerical tools could be used for the material design of stents}, language = {en} } @misc{DahmaniFellahHeziletal., author = {Dahmani, Marwa and Fellah, Mamoun and Hezil, Naouel and Benoudia, Mohamed-Cherif and Obrosov, Aleksei and El-Hiti, Gamal A. and Weiß, Sabine}, title = {Bioactivity and tribological performance of a novel nano-biomaterial beta-type Ti-alloy}, series = {Journal of materials research and technology}, volume = {36}, journal = {Journal of materials research and technology}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2214-0697}, doi = {https://doi.org/10.1016/j.jmrt.2025.03.180}, pages = {2297 -- 2316}, abstract = {This study investigates the bioactivity; wear performance, and topography of a novel beta-type titanium-based alloy using techniques such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and 2D and 3D analysis. The tribological test was evaluated using a ball-on-disk tribometer in a wet environment. Different loads of 2, 6, and 10 N were applied during the evolution. The data results indicate a significant effect of the milling process on the formation of the hydroxyapatite layer on the surfaces of the Ti-Nb-Mo alloy. Both the wear volume and rate showed a consistent trend of decrease as the milling time increased from 2 to 12 h for all applied loads. The minimum values of wear and volume were reached after 12 h of milling. The improvement in tribological behavior can be attributed to the improved mechanical properties of the alloys. In addition, the significant presence of niobium (Nb) and molybdenum (Mo) plays a critical role in achieving high coefficient of friction values. The primary wear mechanism observed in the Ti-25Nb-25Mo system was adhesive wear in addition to abrasive wear. With its lower Young's modulus and favorable biological and tribological properties, the Ti-25Nb-25Mo alloy represents a promising option for bone tissue applications in orthopedics.}, language = {en} } @misc{EmdadiJenschSzyndleretal., author = {Emdadi, Aliakbar and Jensch, Felix and Szyndler, Joanna and Huang, Hsuan-Po and H{\"a}rtel, Sebastian and Weiß, Sabine}, title = {Void closure behavior during hot forming of an Fe-Al alloy}, series = {Materials research proceedings}, volume = {54}, journal = {Materials research proceedings}, publisher = {IWA Publishing}, address = {Millersville, PA}, isbn = {978-1-64490-359-9}, issn = {2474-395X}, doi = {10.21741/9781644903599-99}, pages = {927 -- 935}, abstract = {Hot forging is a forming process that can be used as a post-processing treatment to close residual porosity and refine the microstructure of additively manufactured materials, resulting in improved mechanical properties. During hot forging, void closure occurs through plastic deformation resulting from a predominantly compressive stress state at elevated temperatures. In the present work, Fe-25Al-1.5Ta (at. \%) samples have been produced by laser powder bed fusion (LPBF) using a larger layer thickness and scan speed than commonly used to achieve a target porosity fraction of approximately 10\%. Full densification is attempted in the subsequent hot compression step at various height reduction ratios. The as-built LPBF samples contained 8-10\% voids. After deformation to true strains of 0.2, 0.4, and 0.6, the void fraction decreased significantly to approximately 4\%, 2.3\%, and 1.1\%, respectively. Hot compression resulted in the complete closure of large pores with a size range of 200-300 µm and a significant reduction in the size of small to medium pores. These results show potential for improving the productivity of the LPBF by speeding up the process by increasing layer thickness and scanning speed while maintaining a reasonable density. Full densification should be achieved by subsequent hot forging.}, language = {en} } @misc{ErtugrulEmdadiJedynaketal., author = {Ertugrul, G{\"o}khan and Emdadi, Aliakbar and Jedynak, Angelika and Weiß, Sabine and H{\"a}rtel, Sebastian}, title = {Hot forming behavior of tungsten carbide reinforced Ni-based superalloy 625 additively manufactured by laser directed energy deposition}, series = {Additive manufacturing letters}, volume = {13}, journal = {Additive manufacturing letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2772-3690}, doi = {10.1016/j.addlet.2025.100267}, pages = {1 -- 12}, abstract = {The demands of high-performance industries such as aerospace, automotive, tool manufacturing, oil, and gas industries are driving the innovation in high-performance materials and their production methods. This study explores the impact of hybrid manufacturing, specifically the effect of the addition of tungsten carbide (WC/W2C) via Laser-Directed Energy Deposition (L-DED), on the hot workability, hardness, and microstructure of nickel-based superalloy Inconel 625 (IN625). IN625 is known for its high temperature and high corrosion resistance, and tungsten carbide for its high wear resistance and grain refinement effect. The integration of WC/W2C particles into the IN625 matrix, in addition to the use of the hybrid approach of additive manufacturing followed by a hot-forming process, significantly influences the microstructure and mechanical behavior of the material. Thus, while incorporation of the WC/W2C can strengthen the material and extend the mechanical limitations, its full impact, including any potential usages, should be thoroughly evaluated for the intended application of the materials. To understand the effect of WC/W2C, additive manufacturing of IN625 both with and without WC/W2C and isothermal hot compression was carried out. The objective is to analyze the differences in microstructure and properties between L-DED manufactured IN625, and WC-reinforced IN625, and their hot-forming behavior, focusing on the effects of WC addition and post-deformation on microstructure and mechanical properties. This work represents the first investigation into the effect of WC/W2C hard particles on the hot-forming process of additively manufactured Ni-based metal matrix composites.}, language = {en} } @misc{EmdadiBolzJenschetal., author = {Emdadi, Aliakbar and Bolz, Sebastian and Jensch, Felix and Tovar, Michael and Weiß, Sabine}, title = {On the hot deformation of a Fe-Al-Ta iron aluminide prepared via laser powder bed fusion}, series = {Crystals}, volume = {13}, journal = {Crystals}, number = {4}, publisher = {MDPI}, address = {Basel}, issn = {2073-4352}, doi = {10.3390/cryst13040627}, pages = {1 -- 12}, abstract = {In the present work, a combined process of laser powder bed fusion (LPBF) and hot working in terms of microstructure refinement was investigated for Fe-25Al-1.5Ta alloy samples. Uniaxial compression tests were carried out parallel and perpendicular to the building direction (BD) at 1000 °C, where BCC A2-phase was stable, at a strain rate of 0.0013 s-1. The true stress-true strain curves indicated a broad flow stress peak followed by a slight decrease, which is typical for dynamic recrystallization (DRX) of conventional BCC metals such as ferritic iron. A negligible dependence in the flow stress behavior on the compression direction was observed. DRX initiated at a stress of 18.7 MPa for the sample compressed parallel to the BD, corresponding to a true strain of 0.011, and at 18.1 MPa for the samples compressed normal to the BD, which corresponded to a true strain of 0.010. The microstructural investigations by electron backscatter diffraction (EBSD) showed that the relatively coarse and elongated grains of the as-LPBF builds were significantly refined after hot working. The microstructure of the compressed samples mainly consisted deformed grains. These were fragmented by sub-grains bounded by low-angle boundaries independent of the compression axis, indicating the occurrence of dynamic recovery (DRV) during hot working. In addition, a few equiaxed, small grains were observed in the pre-existing grain boundaries, which formed due to DRX. Most pores in the as-LPBF builds were closed after hot compression, particularly in the central region of the deformed specimens where the compressive stress state is dominant. In summary, hot compression reveals a practical thermomechanical post-processing treatment for Fe-Al-Ta iron aluminides built by LPBF. The hot working refines the epitaxially elongated microstructure of the as-LPBF builds by DRV/DRX and reduces the porosity.}, language = {en} } @misc{EmdadiYangSzyndleretal., author = {Emdadi, Aliakbar and Yang, Yitong and Szyndler, Joanna and Jensch, Felix and Ertugrul, G{\"o}khan and Tovar, Michael and H{\"a}rtel, Sebastian and Weiß, Sabine}, title = {Highly printable Fe₃Al intermetallic alloy}, series = {Metals : open access journal}, volume = {16}, journal = {Metals : open access journal}, number = {5}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/met16010005}, pages = {1 -- 15}, abstract = {Intermetallic Fe₃Al-based alloys reinforced with Laves-phase precipitates are emerging as potential replacements for conventional high-alloy steels and possibly polycrystalline Ni-based superalloys in structural applications up to 700 °C. Their impressive mechanical properties, however, are offset by limited fabricability and poor machinability due to their severe brittleness. High tool wear during finish-machining, which is still required for components such as turbine blades, remains a key barrier to their broader adoption. In contrast to conventional manufacturing routes, additive manufacturing offers a viable solution by enabling near-net-shape manufacturing of difficult-to-machine iron aluminides. In the present study, laser powder bed fusion was used to produce an Fe-25Al-1.5Ta intermetallic containing strengthening Laves-phase precipitates, and the porosity, microstructure and phase composition were characterized as a function of the process parameters. The results showed that preheating the build plate to 650 °C effectively suppressed delamination and macrocrack formation, even though noticeable cracking still occurred at the high scan speed of 1000 mm/s. X-ray tomography revealed that samples fabricated with a lower scan speed (500 mm/s) and a higher layer thickness (0.1 mm) contained larger, irregularly shaped pores, whereas specimens printed at the same volumetric energy density (40 J/mm3) but with different parameter sets exhibited smaller fractions of predominantly spherical pores. All samples contained mostly elongated grains that were either oriented close to <001> relative to the build direction or largely texture-free. X-ray diffraction confirmed the presence of Fe₃Al and C14-type (Fe, Al)₂Ta Laves phase in all samples. Hardness values fell within a narrow range (378-398 HV10), with only a slight reduction in the specimen exhibiting higher porosity.}, language = {en} } @misc{JenschSviridovDubininetal., author = {Jensch, Felix and Sviridov, Alexander and Dubinin, Sergej and Karabulut, Fatih and Weiß, Sabine and H{\"a}rtel, Sebastian}, title = {Parameter optimization for low-porosity Ti-6Al-4V parts produced using accelerated PBF-LB process}, series = {Progress in additive manufacturing}, journal = {Progress in additive manufacturing}, publisher = {Springer}, address = {Cham}, issn = {2363-9520}, doi = {10.1007/s40964-025-01510-w}, pages = {1 -- 17}, abstract = {In this study, the influence of various process parameters on the porosity of Ti-6Al-4V parts fabricated via Powder Bed Fusion - Laser Based (PBF-LB) is investigated. Three different layer thicknesses (30 μm, 60 μm, and 120 μm) were analyzed to define process windows enabling a build-rate acceleration while keeping the porosity below 0.1\%. Through iterative parameter refinement, the effects of laser power, scan speed and hatch distance were examined in terms of linear energy density (LED), energy transmission density (ETD) and volumetric energy density (VED), and their influence on the formation of process-related defects such as pores. Correlations between these energy metrics and pore formation types (keyhole vs. lack-of-fusion) are discussed. The results demonstrate that process acceleration by a factor of more than 3 is possible while maintaining high quality of the components in terms of internal porosity. In addition, an accelerated method for manufacturing components using the PBF-LB process is presented, in which components are manufactured at very high build-rates but with increased porosity and then brought to the target porosity of 0.1\% using the HIP process. This has made it possible to accelerate the build-rate in PBF-LB production by a further 32\%. Accounting for the additional time required for HIP, the HIP route is faster than using the accelerated, which achieves the target porosity in as-built condition, for parts larger than 1421 cm3.}, language = {en} }