TY - GEN A1 - Morozova, Iuliia A1 - Królicka, Aleksandra A1 - Obrosov, Aleksei A1 - Yang, Yitong A1 - Doynov, Nikolay A1 - Weiß, Sabine A1 - Michailov, Vesselin T1 - Precipitation phenomena in impulse friction stir welded 2024 aluminium alloy T2 - Materials Science and Engineering: A N2 - 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. KW - AA2024 KW - impulse friction stir welding KW - microhardness KW - s precipitation KW - thermal cycle KW - deformation Y1 - 2022 U6 - https://doi.org/10.1016/j.msea.2022.143617 SN - 0921-5093 SP - 1 EP - 11 ER - TY - GEN A1 - Figiel, Paweł A1 - Biedunkiewicz, Anna A1 - Jach, Katarzyna A1 - Obrosov, Aleksei A1 - Garbiec, Dariusz A1 - Bik, Maciej A1 - Sitarz, Maciej A1 - Kucia, Zofia A1 - Pawlyta, Mirosława A1 - Weiß, Sabine T1 - Ti-Mo-xTiC composites manufactured by U-FAST reactive sintering T2 - International Journal of Refractory Metals and Hard Materials N2 - 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. KW - TiMMCs KW - SPS KW - EBSD KW - Nanoindentation KW - Wear Y1 - 2022 UR - https://www.sciencedirect.com/science/article/pii/S0263436822001846#! U6 - https://doi.org/10.1016/j.ijrmhm.2022.105960 SN - 0263-4368 IS - 108 SP - 1 EP - 14 ER - TY - GEN A1 - Petkov, Nikolay A1 - Bakalova, Totka A1 - Obrosov, Aleksei A1 - Kashkarov, Egor B. A1 - Kormunda, Martin A1 - Kejzlar, Pavel A1 - Bahchedzhiev, Hristo A1 - Dadourek, Karel A1 - Weiß, Sabine T1 - Structural, mechanical, and tribological properties of CrCN coatings obtained by cathodic arc physical vapour deposition technology at different CH4/N2 gas ratio T2 - Thin Solid Films N2 - 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. KW - Chromium carbonitride KW - Cathodic arc deposition KW - X-ray diffraction KW - X-ray photoelectron spectroscopy KW - Mechanical properties KW - Wear Y1 - 2023 UR - https://www.sciencedirect.com/science/article/pii/S0040609022005715 U6 - https://doi.org/10.1016/j.tsf.2022.139669 SN - 1879-2731 VL - 766 ER - TY - GEN A1 - Grudinin, V. A. A1 - Bleykher, G. A. A1 - Krivobokov, V. P. A1 - Semyonov, O. V. A1 - Obrosov, Aleksei A1 - Weiß, Sabine A1 - Sidelev, D. V. T1 - Hot target magnetron sputtering enhanced by RF-ICP source: Microstructure and functional properties of CrNx coatings T2 - Vacuum N2 - 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. KW - CrN KW - Coatings KW - Hot target KW - Magnetron sputtering KW - High-rate deposition KW - RF-ICP Y1 - 2022 UR - https://www.sciencedirect.com/science/article/pii/S0042207X2200152X U6 - https://doi.org/10.1016/j.vacuum.2022.111020 SN - 1879-2715 VL - 200 ER - TY - GEN A1 - Alontseva, Darya A1 - Safarova (Yantsen), Yuliya A1 - Voinarovych, Sergii A1 - Obrosov, Aleksei A1 - Yamanoglu, Ridvan A1 - Khoshnaw, Fuad A1 - Yavuz, Hasan Ismail A1 - Nessipbekova, Assem A1 - Syzdykova, Aizhan A1 - Azamatov, Bagdat A1 - Khozhanov, Alexandr A1 - Weiß, Sabine T1 - Biocompatibility and Corrosion of Microplasma-Sprayed Titanium and Tantalum Coatings versus Titanium Alloy T2 - Coatings N2 - 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. KW - biocompatible coatings KW - in vitro test KW - corrosion resistance KW - microplasma spraying (MPS) KW - medical implants KW - coating techniques Y1 - 2024 UR - https://www.mdpi.com/2079-6412/14/2/206 U6 - https://doi.org/10.3390/coatings14020206 SN - 2079-6412 VL - 14 IS - 2 ER - TY - GEN A1 - Fellah, Mamoun A1 - Hezil, Naouel A1 - Bouras, Dikra A1 - Bouchareb, Nabila A1 - Larios, Alejandro Perez A1 - Obrosov, Aleksei A1 - El-Hiti, Gamal A. A1 - Weiß, Sabine T1 - 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 T2 - Journal of Science: Advanced Materials and Devices N2 - 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. KW - Ti-Nb-Zr alloys KW - Nanobiomaterials KW - Tribological behavior KW - Corrosion KW - Ringer's solution KW - Biomedical applications Y1 - 2024 UR - https://www.sciencedirect.com/science/article/pii/S2468217924000261 U6 - https://doi.org/10.1016/j.jsamd.2024.100695 SN - 2468-2179 ER - TY - GEN A1 - Fellah, Mamoun A1 - Bouchareb, Nabila A1 - Hezil, Naouel A1 - Merah, Neçar A1 - Alashkar, Yasser A1 - Imran, Mohd A1 - Obrosov, Aleksei A1 - Weiß, Sabine T1 - Electrochemical analysis of mechanically alloyed Ti50%-Ni50% alloy for bone implants use T2 - Journal of Alloys and Compounds N2 - 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 Å, 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. KW - Ti-Ni alloys KW - Biomaterials KW - Mechanical alloying KW - Nanomaterial KW - Corrosion behavior KW - Electrochemical impedance spectroscopy Y1 - 2025 U6 - https://doi.org/https://doi.org/10.1016/j.jallcom.2024.178046 SN - 1873-4669 IS - 1010 SP - 1 EP - 13 ER - TY - GEN A1 - Alontseva, Darya A1 - Safarova (Yantsen), Yuliya A1 - Voinarovych, Sergii A1 - Obrosov, Aleksei A1 - Yamanoglu, Ridvan A1 - Khoshnaw, Fuad A1 - Nessipbekova, Assem A1 - Syzdykova, Aizhan A1 - Yavuz, Hasan Ismail A1 - Kaliuzhnyi, Sergii A1 - Krasavin, Alexander A1 - Azamatov, Bagdat A1 - Khozhanov, Alexandr A1 - Olzhayev, Farkhad A1 - Weiß, Sabine T1 - Microplasma-Sprayed Titanium and Hydroxyapatite Coatings on Ti6Al4V Alloy: in vitro Biocompatibility and Corrosion Resistance: Part I T2 - Johnson Matthey Technology Review N2 - 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. KW - Endoprosthesis implants KW - Biocompatible coatings KW - Porosity KW - Surface roughness KW - In vitro test KW - Elastic modulus Y1 - 2025 UR - https://technology.matthey.com/content/journals/10.1595/205651325X17201903387613 U6 - https://doi.org/10.1595/205651325X17201903387613 VL - 69 IS - 1 SP - 45 EP - 58 ER - TY - GEN A1 - Alontseva, Darya A1 - Safarova (Yantsen), Yuliya A1 - Voinarovych, Sergii A1 - Obrosov, Aleksei A1 - Yamanoglu, Ridvan A1 - Khoshnaw, Fuad A1 - Nessipbekova, Assem A1 - Syzdykova, Aizhan A1 - Yavuz, Hasan Ismail A1 - Kaliuzhnyi, Sergii A1 - Krasavin, Alexander A1 - Azamatov, Bagdat A1 - Khozhanov, Alexandr A1 - Olzhayev, Farkhad A1 - Weiß, Sabine T1 - 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 T2 - Johnson Matthey Technology Review N2 - 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. KW - Endoprosthesis implants KW - Biocompatible coatings KW - Porosity KW - Surface roughness KW - In vitro test KW - Elastic modulus Y1 - 2025 U6 - https://doi.org/10.1595/205651325X17290035905758 SN - 2056-5135 VL - 69 (2025) IS - 1 SP - 59 EP - 75 ER - TY - GEN A1 - Synodinos, Alexis D. A1 - Karnatak, Rajat A1 - Aguilar‐Trigueros, Carlos A. A1 - Gras, Pierre A1 - Heger, Tina A1 - Ionescu, Danny A1 - Maaß, Stefanie A1 - Musseau, Camille L. A1 - Onandia, Gabriela A1 - Planillo, Aimara A1 - Weiss, Lina A1 - Wollrab, Sabine A1 - Ryo, Masahiro T1 - The rate of environmental change as an important driver across scales in ecology T2 - Oikos N2 - 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. KW - climate change KW - ecological communities KW - eco-evo feedbacks KW - transitions KW - global change KW - R-tipping KW - temporal ecology Y1 - 2023 U6 - https://doi.org/10.1111/oik.09616 SN - 0030-1299 VL - 2023 IS - 4 PB - Wiley ER - TY - GEN A1 - Yang, Yitong A1 - Weiß, Sabine T1 - In-situ investigation on cyclic bending deformation of oligocrystalline 316LVM steel for coronary stent application with EBSD T2 - International Conference on Strength of Materials 2022 N2 - 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. KW - Oligo-crystalline microstructure, in-situ bending fatigue test, EBSD, 316LVM austenitic steel, coronary stent, Y1 - 2022 UR - https://hal.science/hal-03829658v1 PB - HAL open science ER -