TY - CONF A1 - Olbricht, Jürgen A1 - Agudo Jácome, Leonardo A1 - Jürgens, Maria A1 - Roohbakhshan, Farshad A1 - Fedelich, Bernard A1 - Skrotzki, Birgit T1 - Cyclic loading performance and related microstructure evolution of ferritic-martensitic 9-12% Cr steels N2 - The current competitive situation on electricity markets forces power plants into cyclic operation regimes with frequent load shifts and starts/shutdowns. In the present work, the cyclic mechanical behavior of ferritic-martensitic 9-12 % Cr steels under isothermal and thermomechanical loading was investigated for the example of grade P92 material. A continuous softening was observed under all loading conditions. The introduction of hold periods to the applied cycles reduced material lifetime, with most prominent effects at technologically relevant small strain levels. The microstructural characterization reveals a coarsening of the original “martensitic” lath-type microstructure to a structure with polygonal subgrains and reduced dislocation density. The microstructural data forms the input for a physically-based modelling approach. T2 - 44th MPA-Seminar CY - Leinfelden/Stuttgart, Germany DA - 17.10.2018 KW - Ferritic-martensitic steels KW - Cyclic loading KW - Microstructure evolution PY - 2018 SP - 259 EP - 265 AN - OPUS4-47118 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Häusler, Ines A1 - Darvishi Kamachali, Reza A1 - Hetaba, W. A1 - Skrotzki, Birgit T1 - Thickening of T-1 Precipitates during Aging of a High Purity Al–4Cu–1Li–0.25Mn Alloy N2 - The age hardening response of a high-purity Al–4Cu–1Li–0.25Mn alloy (wt. %) during isothermal aging without and with an applied external load was investigated. Plate shaped nanometer size T1 (Al2CuLi) and θ′ (Al2Cu) hardening phases were formed. The precipitates were analyzed with respect to the development of their structure, size, number density, volume fraction and associated transformation strains by conducting transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) studies in combination with geometrical Phase analysis (GPA). Special attention was paid to the thickening of T1 phase. Two elementary types of single-layer T1 precipitate, one with a Li-rich (Type 1) and another with an Al-rich (Defect Type 1) central layer, were identified. The results show that the Defect Type 1 structure can act as a precursor for the Type 1 structure. The thickening of T1 precipitates occurs by alternative stacking of These two elementary structures. The thickening mechanism was analyzed based on the magnitude of strain associated with the precipitation transformation normal to its habit plane. Long-term aging and aging under load resulted in thicker and structurally defected T1 precipitates. Several types of defected precipitates were characterized and discussed. For θ′ precipitates, a ledge mechanism of thickening was observed. Compared to the normal aging, an external load applied to the peak aged state leads to small variations in the average sizes and volume fractions of the precipitates. KW - Al-Cu-Li-alloy KW - Precipitation KW - T1 precipitate KW - Microstructure evolution KW - Thickening KW - Creep KW - Volume fraction KW - Number density KW - Strain difference PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-471207 DO - https://doi.org/10.3390/ma12010030 SN - 1996-1944 VL - 12 IS - 1 SP - 30, 1 EP - 23 PB - MDPI AN - OPUS4-47120 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sommer, Konstantin A1 - Kranzmann, Axel A1 - Reimers, W. T1 - Microstructure characterization of additive produced parts N2 - Due to the advantages of additive manufacturing (AM), it has been increasingly integrated into many industrial sectors. The application of AM materials for safety-critical parts requires the detailed knowledge about their microstructure stability under thermo-mechanical or mechanical load and knowledge on ageing process mechanisms. Ageing processes are characterized by change of the material microstructure that is to be initially investigated. This work deals with the Investigation of 316L stainless steel manufactured by selective laser melting (SLM). Describing Parameters must be defined and applied on the microstructure of these materials in their initial state and after loads were applied. The findings of this work form the basis for the investigation of AM material ageing. T2 - FEMS Junior EUROMAT 2018 CY - Budapest, Hungary DA - 08.07.2018 KW - Additive manufacturing KW - Selective laser melting KW - 316L KW - Material characterization KW - Microstructure PY - 2018 AN - OPUS4-47176 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gesell, Stephan T1 - WP8 - RCS standardisation work N2 - The presentation presents a first work premise for the acceptable failrate of a hydrogen pressure vessel. Based on this premise, the basic algorithm for the analysis of given acceptance criteria is presented. T2 - TAHYA PSB Meeting#1 CY - TU Chemnitz, Germany DA - 20.11.2018 KW - FCH JU KW - TAHYA KW - Horizon 2020 KW - Safety assessment PY - 2018 AN - OPUS4-47178 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Roohbakhshan, Farshad A1 - Olbricht, Jürgen A1 - Fedelich, Bernard A1 - Skrotzki, Birgit T1 - Dislocation-based modeling of high temperature deformation and fatigue in P92 ferritic-martensitic steels N2 - The employment of renewable energy resources, which are naturally intermittent, for electricity generation has altered the working conditions of conventional power plants from continuous (baseload) to cyclic or flexible operation. For a long time, 9-12% Cr ferritic-martensitic stainless steels have been widely used in power plants due to their favorable characteristics such as high creep strength at high temperatures and oxidation and corrosion resistance. The components of power plants are subjected to long term cyclic loadings including fatigue and creep-fatigue at high temperatures. As ferritic-martensitic steels are known to exhibit cyclic softening when subjected to such loading scenarios, it is crucial to study the material response in such conditions. Since it is impossible to test the material behavior exactly as the operation conditions of power plants, due to technical difficulties and cost issues, it is necessary to develop physically-based material models that can predict the material behavior in more realistic situations. In recent years, many material models have been proposed to describe the behavior of 9-12% Cr ferritic-martensitic stainless steels, which follow phenomenological or physically-based approaches. Phenomenological models provide a stress-strain relation based on empirical observations although they usually lack physical background. To alleviate this drawback and to allow for more flexibility and wider ranges of strain-rate and temperature, physically-based models are suggested. In this approach, microstructural evolution, dislocation movement and/or kinetics of plastic deformation processes are included. The physically-based models allow for a better extrapolation from the experiment results to other operation conditions and their material constants can be interpreted physically. Compared to the former approach, the material behavior can be described more accurately and flexibly and the number of material constants is less in general. In the presented work, the existing micromechanical models developed for P92 steel are compared and extended to allow for new dislocation-based strengthening/cyclic mechanisms. Their performance is assessed in the light of mechanical test data from creep-fatigue and thermo-mechanical fatigue experiments and detailed characterizations of the microstructure evolution in the fatigued material. T2 - 12th International Fatigue Congress CY - Poitiers, France DA - 27.05.2018 KW - 9-12% Cr ferritic-martensitic steels KW - Cyclic softening KW - Micromechanical model KW - Microstructural evolution KW - P92 steels PY - 2018 AN - OPUS4-47101 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Skrotzki, Birgit A1 - Uckert, Danilo A1 - Kühn, Hans-Joachim A1 - Matzak, Kathrin A1 - Rehmer, Birgit T1 - Ermüdungsverhalten des warmfesten austenitischen Gusseisens EN-GJSA-XNiSiCr35-5-2 bei hoher Temperatur N2 - Die warmfeste austenitische Gusseisenlegierung EN-GJSA-XNiSiCr35-5-2 (häufig auch als Ni-Resist D-5S bezeichnet) wurde hinsichtlich ihres mechanischen Verhal-tens bei hoher Temperatur charakterisiert. Dazu wurden (isotherme) niederzyklische (LCF-) und (nicht-isotherme) thermomechanische Ermüdungsversuche (TMF) zwischen Raumtemperatur und 900 °C durchgeführt. Diese Ergebnisse dienten (zu-sammen mit weiteren Versuchsdaten) der Kalibrierung werkstoffmechanischer Modelle. Bei den höchsten Prüftemperaturen wurde Schädigung in Form von Kriechen beobachtet und metallographisch dokumentiert. T2 - 41. Vortragsveranstaltung Langzeitverhalten warmfester Stähle und Hochtemperaturwerkstoffe CY - Dusseldorf, Germany DA - 30.11.2018 KW - Ni-Resist KW - LCF KW - TMF KW - Kriechen KW - Lebensdauer KW - Schädigung PY - 2018 AN - OPUS4-46851 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Müller, Alexander T1 - Schädigungscharakterisierung an Faser-Kunststoff-Verbunden im Schwingversuch mittels Röntgenrefraktionstopographie unter Berücksichtigung der Matrixeigenschaften N2 - In der vorliegenden Arbeit wurden verschiedene Epoxidharzsysteme charakterisiert. Zwei Systeme mit großen bruchmechanischen Unterschieden wurden zur Fertigung äquivalenter GFK- und CFK-Laminate mit Faserausrichtungen in 0/90° und ±45° ausgewählt. In quasi-statischen Zugversuchen und Einstufenschwingversuchen mit einem Beanspruchungsverhältnis von R= 0,1 wurden diese Laminate hinsichtlich ihres Schädigungsbeginns und ihrer Schädigungsentwicklung untersucht. Die Detektion der Schädigungen sowie die Dokumentation der Schädigungsentwicklung wurde anhand der Lichtabsorptionsanalyse an GFK-Laminaten und anhand der Röntgenrefraktionsanalyse an CFK-Laminaten umgesetzt. Auf diese Weise konnten Einflüsse der bruchmechanischen Eigenschaften der Matrix auf die Schädigungsentwicklung im Verbund aufgezeigt werden. Zudem wurden für die untersuchten Laminate die Schädigungsgrenzen bei schwingender Beanspruchung ermittelt. Anhand durchgeführter Schwingversuche an CFK-Laminaten im Very High Cycle Fatigue-(VHCF)-Lastwechselbereich bis 108 konnten Rückschlüsse vom Schädigungsverhalten im High Cycle Fatigue-(HCF)-Lastwechselbereich bis 106 auf die Dauerfestigkeit im VHCF-Bereich gezogen werden und damit VHCF-Dauerfestigkeitsgrenzen bestimmt werden. Mit dem Ziel die Ermüdung der Laminate auf die Beanspruchung der Matrix zurückzuführen, wurden die Erweiterte Inverse Laminattheorie, mikromechanikbasierte Mischungsregeln sowie eine Vergleichsspannungshypothese auf die untersuchten Laminate angewendet. Die Schädigungsgrenzen konnten damit in Form der Matrixbeanspruchung wiedergegeben werden. Die Abbildung der Ermüdung verschiedener Laminate anhand einer matrixspezifischen normierten Masterschädigungslinie ist für die behandelten CFK- und GFK-Laminate gelungen. T3 - BAM Dissertationsreihe - 162 KW - CFK KW - GFK KW - Ermüdung KW - Epoxidharz KW - Masterschädigungslinie KW - Röntgenrefraktion KW - ZfP PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-467833 SN - 1613-4249 VL - 162 SP - 1 EP - 204 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-46783 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bresch, Sophie A1 - Mieller, Björn A1 - Delorme, F. A1 - Chen, C. A1 - Bektas, M. A1 - Moos, R. A1 - Rabe, Torsten T1 - Influence of Reaction-Sintering and Calcination Conditions on Thermoelectric Properties of Sm-doped Calcium Manganate CaMnO3 N2 - A wide range of solid-state synthesis routes for calcium manganate is reported in the literature, but there is no systematic study about the influence of the solid-state synthesis conditions on thermoelectric properties. Therefore, this study examined the influence of calcination temperature and calcination cycles on the Seebeck coefficient, electrical conductivity, and thermal conductivity. Higher calcination temperatures and repeated calcination cycles minimized the driving force for sintering of the synthesized powder, leading to smaller shrinkage and lower densities of the sintered specimens. As the electrical conductivity increased monotonously with increasing density, a higher energy input during calcination caused deterioration of electrical conductivity. Phase composition and Seebeck coefficient of sintered calcium manganate were not influenced by the calcination procedure. The highest thermoelectric properties with the highest power factors and figures of merit were obtained by means of reaction-sintering of uncalcined powder. KW - Thermoelectric oxides KW - Calcination KW - Solid-state-synthesis KW - Power factor KW - Reaction-sintering PY - 2018 DO - https://doi.org/10.4416/JCST2018-00017 SN - 2190-9385 VL - 9 IS - 3 SP - 289 EP - 300 PB - Göller Verlag AN - OPUS4-46224 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Höhne, Patrick A1 - Mieller, Björn A1 - Rabe, Torsten T1 - Slurry development for spray granulation of ceramic multicomponent batches N2 - The granules commonly yielded by spray drying procedures exhibit a hard shell and an irregular, dimpled shape, which is often described as donut-like morphology. Sintered parts produced from such granules suffer from microstructural defects and reduced mechanical properties resulting from these disadvantageous granule properties. Using the example of alumina, zirconia and zirconia-toughened alumina (ZTA) batches, this paper shows that the morphology of the granules can be tuned by adjusting slurry stability. High zeta potential is essential to optimally disperse the particles. But to achieve spherical and soft granules the electrostatic repulsion forces between the particles should be reduced before spray granulation. Electrostatic repulsion forces were changed with the addition of nitric acid. Measurements of zeta potential and viscosity, as well as sedimentation investigations with an optical centrifuge were used for precise slurry assessment as a major precondition for optimal and reproducible adjustment of slurries before spray drying. Sedimentation analysis using an optical centrifuge was performed to investigate different influences like that of additive composition, solids content or pH-value on the sedimentation behavior. Adequately flocculated slurries lead to homogeneous, soft granules that can be easily deformed and pressed. The fraction of donut-shaped particles and the rigidity of granules were reduced. Consequently, the sintered parts produced from these granulates show improvements regarding porosity, pore size distribution, sintered density and biaxial strength. KW - Slurry optimization KW - Optical centrifugation KW - Destabilization KW - Spray drying KW - Biaxial strength PY - 2018 DO - https://doi.org/10.4416/JCST2018-00022 SN - 2190-9385 VL - 9 IS - 3 SP - 327 EP - 336 PB - Göller Verlag AN - OPUS4-46225 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rockenhäuser, Christian A1 - Häusler, Ines A1 - Darvishi Kamachali, Reza A1 - Heidl, Daniel A1 - Skrotzki, Birgit T1 - Influence of heat treatment and creep loading on an Al-Cu-Li alloy N2 - The influence of heat treatment and creep loading on the microstructure of an Al-Cu-Li alloy was investigated. Especially the formation of different precipitates (T1 and Theta') were characterized and the microstructural changes under different ageing conditions (with and without external strain) were investigated to determine the effect od stress on the ageing process. T2 - 19th International Microscopy Congress (IMC19) CY - Sydney, Australia DA - 09.09.2018 KW - Aluminium KW - Degradation KW - Coarsening KW - Dark-field transmission electron microscopy PY - 2018 AN - OPUS4-46129 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -