TY - JOUR A1 - Peter, D. A1 - Pfetzing, J. A1 - Wagner, M.F.-X. A1 - Somsen, C. A1 - Pesicka, J. A1 - Skrotzki, Birgit A1 - Eggeler, G. T1 - Quantitative Charakterisierung der Gefüge-Anisotropie einer stranggepressten TiAl-Legierung / Quantitative Characterisation and Microstructural Anisotropy of a Hot-Extruded TiAl Alloy KW - Titanaluminide KW - Mikrostruktur KW - Quantitative Analyse KW - Kriechen KW - Anisotropie PY - 2008 SN - 0032-678X N1 - Sprachen: Deutsch/Englisch - Languages: German/English VL - 45 IS - 5 SP - 210 EP - 224 PB - Hanser CY - München AN - OPUS4-17562 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sturm, D. A1 - Heilmaier, M. A1 - Schneibel, J.H. A1 - Jéhanno, P. A1 - Skrotzki, Birgit A1 - Saage, H. T1 - The influence of silicon on the strength and fracture toughness of molybdenum N2 - Mo–Si alloys containing up to 1 wt.% Si were fabricated by powder-metallurgical processing and their lattice parameters, elastic constants, densities, grain sizes, strengths, ductilities, and fracture toughness values were measured. The yield strength was insensitive to the grain size, i.e., a Hall–Petch relationship was not observed. Generally, Si additions caused pronounced solid solution strengthening. However, for small Si concentrations (≤0.1 wt.%) solid solution softening was observed at room temperature and below. With increasing Si concentration, the room temperature ductility and fracture toughness dropped precipitously. This is attributed to the increase in strength and a transition from transgranular to intergranular fracture. KW - Molybdenum KW - Solid solution strengthening KW - Solid solution softening KW - Hall-Petch relationship PY - 2007 SN - 0921-5093 SN - 1873-4936 VL - 463 IS - 1-2 SP - 107 EP - 114 PB - Elsevier CY - Amsterdam AN - OPUS4-14820 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Olbricht, Jürgen A1 - Bismarck, Marc A1 - Skrotzki, Birgit T1 - Characterization of the creep properties of heat resistant 9-12% chromium steels by miniature specimen testing N2 - A miniature specimen geometry is presented that allows to extract small samples for tensile creep tests directly from critical components of steam generators in power plants like e.g. superheater tubes. In this way, material can be tested which has been subjected to the full processing chain of the component. The specimens then exhibit all microstructural modifications that are present in the component after the shaping process and heat treatment, and representative mechanical properties are determined. Similarly, specimens can be extracted from pre-corroded test pieces or used components after service to determine the impact of complex aging/loading/oxidation conditions during service on the mechanical properties of the material. The applicability of the miniature specimen test method is demonstrated in a comparative creep study involving standard and miniature specimens of P91 tempered martensite ferritic steel. Test results indicate satisfactory accuracy/repeatability of the method. Comparison with large scale specimen data reveals an influence of specimen size on the obtained creep behavior. These size effects need to be considered for a correct interpretation of results from miniature specimen creep tests. KW - Fossil fuel power plants KW - Creep testing KW - Miniature specimen KW - Size effects KW - Tempered martensite ferritic steels KW - P91 PY - 2013 DO - https://doi.org/10.1016/j.msea.2013.07.067 SN - 0921-5093 SN - 1873-4936 VL - 585 SP - 335 EP - 342 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-29080 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brookes, Stephen-Peter A1 - Kühn, Hans-Joachim A1 - Skrotzki, Birgit A1 - Klingelhöffer, Hellmuth A1 - Sievert, Rainer A1 - Pfetzing, J. A1 - Peter, D. A1 - Eggeler, G. T1 - Axial-torsional thermomechanical fatigue of a near-gamma TiAl-alloy N2 - The uniaxial, torsional and axial-torsional thermomechanical fatigue (TMF) behavior of the near-γ TiAl-alloy TNB-V5 was investigated. TMF tests were performed at 400-800 °C with mechanical strain amplitudes ranging from 0.15% to 0.7%. The tests were conducted thermomechanically in-phase (IP) and out-of-phase (OP). For the same lifetimes, uniaxial IP tests required the highest strain amplitudes, while OP test conditions were most damaging and needed the lowest strain amplitudes. The Mises equivalent mechanical strain amplitudes of pure torsional tests were found in between uniaxial in-phase and out-of-phase tests for the same lifetimes. The non-proportional multiaxial out-of-phase test showed a lower lifetime at the same equivalent mechanical strain amplitude compared to the other types of tests. The microstructure has been characterized applying electron microscopy and microstructural parameters such as fraction of twinned grains, grain size, lamellar distance and dislocation density have been quantified. KW - Gamma titanium aluminide KW - TNB-V5 KW - Thermomechanical fatigue (TMF) KW - Axial-torsional loading KW - Microstructure PY - 2010 DO - https://doi.org/10.1016/j.msea.2010.03.073 SN - 0921-5093 SN - 1873-4936 VL - 527 IS - 16-17 SP - 3829 EP - 3839 PB - Elsevier CY - Amsterdam AN - OPUS4-21289 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rehmer, Birgit A1 - Skrotzki, Birgit A1 - Glaubitz, Steffen T1 - Influence of casting skin on fatigue lifetime of ferritic ductile cast iron N2 - The fatigue behaviour of cast iron is usually investigated on machined specimens. Components of cast iron, however, have a casting skin; therefore the investigation of the influence of the casting skin on the lifetime is of interest. To study this influence isothermal fatigue tests were carried out on heat-resisting spheroidal graphite cast iron EN GJS SiMo 4.05 in 4–point-bending set-up at 400 °C. Specimens with and without casting skin were investigated comparatively. The number of cycles to failure was significantly lower for specimens with casting skin. Metallographic investigations underline the reduction of lifetime caused by casting skin. KW - Cast iron KW - Casting skin KW - Fatigue KW - Lifetime PY - 2017 SN - 0025-5300 VL - 59 IS - 1 SP - 5 EP - 10 PB - Carl Hanser Verlag CY - München AN - OPUS4-38929 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bettge, Dirk A1 - Günther, Burkhard A1 - Wedell, Wolfgang A1 - Portella, Pedro Dolabella A1 - Hemptenmacher, J. A1 - Peters, P.W.M. A1 - Skrotzki, Birgit T1 - Mechanical behavior and fatigue damage of a titanium matrix composite reinforced with continuous SiC fibers N2 - A titanium (Ti-6242) matrix composite reinforced with continuous SiC fibers was studied. The mechanical behavior of the matrix and the composite was characterized by tensile, creep and isothermal fatigue tests at room temperature and up to 550°C. The thermo-mechanical fatigue behavior under in-phase and out-of-phase conditions was investigated for the composite between 100 and 550°C. Fracture surfaces were characterized by confocal light microscopy and by scanning electron microscopy to identify the damage mechanisms. KW - Metal matrix composites KW - Tensile strength KW - Creep strength KW - Isothermal fatigue KW - Thermo-mechanical fatigue KW - Damage analysis PY - 2007 SN - 0921-5093 SN - 1873-4936 VL - 452-453 SP - 536 EP - 544 PB - Elsevier CY - Amsterdam AN - OPUS4-14616 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pulz, Robert A1 - Rehmer, Birgit A1 - Skrotzki, Birgit T1 - Thermoschock - Interpretation von makroskopischen Bruchmerkmalen / Thermal shock - an interpretation of the macroscopic characteristics of fracture N2 - Der vorliegende Beitrag beschreibt typische Bruchmuster, die an SSiC Proben nach Thermoschockexperimenten beobachtet wurden und korreliert diese qualitativ mit der aufgebrachten Belastung. Der Thermoschock wird durch eine schnelle, in der Probenmitte beginnende spiralförmige Aufheizung dünner Scheiben mit Laserstrahlung realisiert. Durch diese Versuchsführung wandert ein zunehmender Temperaturgradient von der Mitte beginnend in radialer Richtung durch die Probe. Dieser Temperaturgradient ist für die Ausbildung von Druckspannungen im Probeninneren und Zugspannungen im kalten Randbereich der Probe verantwortlich. Beim Erreichen einer kritischen, versagensrelevanten Spannung tritt Probenbruch auf. Dabei wird die bis zu diesem Zeitpunkt in der Probe gespeicherte elastische Energie teilweise in die Schaffung von Rissoberflächen umgewandelt. Der Zusammenhang zwischen gespeicherter elastischer Energie und Bruchmuster wird dargestellt. KW - Thermoschock KW - Fraktographie KW - Elastische Energie KW - SSiC PY - 2010 DO - https://doi.org/10.3139/147.110081 SN - 0032-678X N1 - Sprachen: Deutsch/Englisch - Languages: German/English VL - 47 IS - 6 SP - 302 EP - 312 PB - Hanser CY - München AN - OPUS4-21515 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nies, Daniel A1 - Pulz, Robert A1 - Glaubitz, Steffen A1 - Finn, Monika A1 - Rehmer, Birgit A1 - Skrotzki, Birgit T1 - Testing of thermal barrier coatings by laser excitation N2 - Thermal barrier coatings (TBCs) are used to increase the operating temperature of land-, sea-, or air-based turbines. As failure of the coating may result in serious damage of the turbine, reliable estimation of the lifetime is essential. Most experiments to assess the lifetime or to determine parameters for simulations of the behavior of TBCs are done by burner-rig-tests, where the operating conditions are simulated by cyclic heating of the surface and cooling of the backside of a coated sample. In this work a possibility is presented to do comparable experiments by heating the surface with laser irradiation instead of a burner. For this purpose a Nd:YAG-laser with a maximum output power of 1?kW and a wavelength of 1064?nm is used. The laser spot can be moved by integrated optics across the sample surface to achieve homogeneous heating of the coating. Cooling of the backside is done by air. The temperature of the sample surface is determined by an infrared-camera which also enables the possibility to detect failures in the coating via thermography. Additionally, acoustic sensors attached to the sample holder are used to detect failures in the sample. The investigated ceramic material (yttria stabilized zirconia) has a very low absorption coefficient at the used laser wavelength. Therefore, a pre-treatment of the samples was needed to increase the absorption coefficient to be able to heat up the samples. In this paper, the experimental setup and first experimental results are presented. KW - Thermal barrier coating (TBC) KW - Yttria stabilized zirconia KW - Laser irradiation KW - Acoustic emission KW - Thermography PY - 2010 DO - https://doi.org/10.1002/adem.201000212 SN - 1438-1656 VL - 12 IS - 12 SP - 1224 EP - 1229 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-22896 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nies, Daniel A1 - Rehmer, Birgit A1 - Skrotzki, Birgit A1 - Vaßen, R. T1 - Damage characterization of thermal barrier coatings by acoustic emission and thermography N2 - Thermal barrier coatings allow increasing the operating temperature and efficiency of land-, sea-, or air-based turbines. As failure of the coating may result in serious damage of the turbine, reliable estimation of its lifetime is essential. To assess the lifetime, cyclic tests are conceived to combine thermal loading by heating the surface of the coating with laser irradiation and nondestructive methods for damage determination. Using laser irradiation allows a high reproducibility of the thermal load. The temperature of the sample surface during thermal loading is determined by an infrared-camera which also enables the possibility to detect damage in the coating via thermography. Additionally, four acoustic sensors, attached to the experimental setup, are used to detect damage in the sample and determine the source of acoustic events. Results of acoustic emission correlate well with thermographic images that visualize the formation and evolution of damage through delaminations in the samples. PY - 2012 DO - https://doi.org/10.1002/adem.201200107 SN - 1438-1656 VL - 14 IS - 9 SP - 790 EP - 794 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-26536 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Olbricht, Jürgen A1 - Lippmann, Tim A1 - Klingelhöffer, Hellmuth A1 - Rehmer, Birgit A1 - Skrotzki, Birgit T1 - Mechanical characterisation of heat resistant power plant materials by creep and fatigue testing in controlled gas atmospheres N2 - The continuing increase of steam parameters of fossil fuelled high efficiency power plants and new combustion concepts for the capture and storage of carbon dioxide lead to harsher service conditions for the components and structural materials of such facilities. The present work introduces a test concept that allows testing of candidate materials under simultaneous mechanical and corrosive loading. The material's reaction can be directly investigated under simulated temperature, load and corrosion conditions of modern installations. First results obtained for different heat resistant steels suggest a strong influence of the environmental medium on the fatigue and creep behaviour. Such findings complement the data that is available from the classical qualification process of the materials and may support the material selection for new power plant installations. N2 - Die weitere Erhöhung der Dampfparameter von hocheffizienten fossil befeuerten Kraftwerken sowie neue Verbrennungskonzepte zur Realisierung der Kohlendioxidabscheidung und -speicherung führen zu erschwerten Einsatzbedingungen für die Bauteile und Strukturwerkstoffe solcher Anlagen. Die vorliegende Arbeit stellt ein Prüfkonzept vor, das die Prüfung von Kandidatenwerkstoffen unter überlagerter mechanischer und korrosiver Beanspruchung ermöglicht. Die Werkstoffreaktion kann direkt unter den simulierten Temperatur-, Last- und Korrosionsbedingungen moderner Anlagen untersucht werden. Erste Ergebnisse für verschiedene warmfeste Stähle deuten auf einen erheblichen Einfluss des Umgebungsmediums auf das Ermüdungs- und Kriechverhalten hin. Solche Erkenntnisse ergänzen die aus den Qualifizierungsuntersuchungen der Werkstoffe verfügbaren Daten und können so die Werkstoffauswahl für neue Anlagen unterstützen. KW - Hocheffiziente Kraftwerke KW - Kohlendioxidabscheidung und -speicherung (CCS) KW - Warmfeste Stähle KW - Mechanische Eigenschaften KW - Korrosionsverhalten KW - High efficiency power plants KW - Carbon capture and storage (CCS) KW - Heat resistant steels KW - Mechanical properties KW - Corrosion behaviour PY - 2014 DO - https://doi.org/10.1002/mawe.201400185 SN - 0933-5137 SN - 1521-4052 VL - 45 IS - 1 SP - 5 EP - 14 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-30309 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -