TY - GEN A1 - Liu, Xu A1 - Song, Lin A1 - Liu, Tong A1 - Stark, Andreas A1 - Pyczak, Florian A1 - He, Zhanbing A1 - Lin, Junpin A1 - Zhang, Tiebang T1 - In- and ex-situ study of the deformation behavior of the βo(ωo) phase in a Ti4Al3Nb alloy during high-temperature compression T2 - Journal of Alloys and Compounds N2 - In-situ synchrotron-based high energy X-ray diffraction (HEXRD) and ex-situ Gleeble tests were conducted to investigate the deformation behavior of the βo(ωo) phase in a Ti4Al3Nb alloy. In samples compressed at 600 and 800 °C, the brittle ωo phase deforms mostly elastically, resulting in the failure of the Ti4Al3Nb alloy by premature fracture. In a sample deformed at 900 °C, the ωo phase mostly transforms into the βo phase under uniaxial loading. Moreover, the ductility of a Ti4Al3Nb alloy is largely enhanced at this temperature. In a sample deformed at 1000 °C, dynamic recrystallization (DRX) of the βo phase extensively takes place. Direction 1 (D1) and Direction 2 (D2) deviating from the loading direction with an angle of 65° ± 5° and 15° ± 5° are selected to analyze the lattice strain evolution of (110)βo lattice planes. At the late stage of macro strain hardening, deformed[removed]βo//D1 oriented grains bear a higher load due to the occurrence of DRX in[removed]βo//D2 oriented grains. Subsequently, DRX continues in[removed]βo//D1 oriented βo grains. The coordinated deformation of βo grains ensures the good deformability of a Ti4Al3Nb alloy at 1000 °C. Y1 - 2022 U6 - https://doi.org/10.1016/j.jallcom.2022.165626 SN - 0925-8388 VL - 918 ER - TY - GEN A1 - Gabrisch, Heike A1 - Janovská, Michaela A1 - Rackel, Marcus W. A1 - Pyczak, Florian A1 - Stark, Andreas T1 - Impact of microstructure on elastic properties in the alloy Ti-42Al-8.5 Nb T2 - Journal of Alloys and Compounds Y1 - 2023 U6 - https://doi.org/10.1016/j.jallcom.2022.167578 SN - 1873-4669 SN - 0925-8388 VL - Vol. 932 ER - TY - GEN A1 - Liu, Xu A1 - Stark, Andreas A1 - Pyczak, Florian A1 - Zhang, Tiebang T1 - In-situ synchrotron high energy X-ray diffraction study on the internal strain evolution of D019-α2 phase during high-temperature compression and subsequent annealing in a TiAl alloy T2 - Journal of Materials Science and Technology Y1 - 2023 U6 - https://doi.org/10.1016/j.jmst.2023.04.027 SN - 1941-1162 SN - 1005-0302 VL - Vol. 163 SP - 212 EP - 222 ER - TY - GEN A1 - Fröbel, Ulrich A1 - Stark, Andreas A1 - Paul, Jonathan A1 - Pyczak, Florian T1 - Assessment of the capability of Zr, Y, La, Gd, Dy, C, and Si to enhance the creep strength of gamma titanium aluminide alloys based on their effect on flow stress and thermal activation parameters T2 - Intermetallics Y1 - 2023 U6 - https://doi.org/10.1016/j.intermet.2023.108018 SN - 1879-0216 SN - 0966-9795 VL - Vol. 162 ER - TY - GEN A1 - Gussone, Joachim A1 - Rackel, Marcus W. A1 - Tumminello, Silvana A1 - Barriobero-Vila, Pere A1 - Kreps, Frederic A1 - Kelm, Klemens A1 - Stark, Andreas A1 - Schell, Norbert A1 - Pyczak, Florian A1 - Haubrich, Jan A1 - Requena, Guillermo T1 - Microstructure formation during laser powder bed fusion of Ti-22Al-25Nb with low and high pre-heating temperatures T2 - Materials and Design Y1 - 2023 U6 - https://doi.org/10.1016/j.matdes.2023.112154 SN - 0264-1275 VL - Vol. 232 ER - TY - GEN A1 - Guo, Xiang A1 - Song, Lin A1 - Liu, Xu A1 - Stark, Andreas A1 - Pyczak, Florian A1 - Zhang, Tiebang T1 - In-situ synchrotron HEXRD study on the phase transformation mechanisms of the ω-related phases in a Ti4Al3Nb alloy T2 - Materials Characterization Y1 - 2023 U6 - https://doi.org/10.1016/j.matchar.2023.112901 SN - 1873-4189 SN - 1044-5803 VL - Vol. 200 ER - TY - GEN A1 - Liu, Xu A1 - Song, Lin A1 - Stark, Andreas A1 - Pyczak, Florian A1 - Zhang, Tiebang T1 - In-situ synchrotron high energy X-ray diffraction study on the deformation mechanisms of D019-α2 phase during high-temperature compression in a TiAl alloy T2 - Journal of Materials Research and Technology Y1 - 2024 U6 - https://doi.org/10.1016/j.jmrt.2024.10.231 SN - 2238-7854 VL - 33 SP - 5850 EP - 5862 PB - Elsevier BV ER - TY - GEN A1 - Liu, Xu A1 - Song, Lin A1 - Pyczak, Florian A1 - Stark, Andreas A1 - Wang, Li A1 - Guo, Xiang A1 - Zhang, Tiebang T1 - Stress-induced orthorhombic O phase in TiAl alloys T2 - Acta materialia N2 - The orthorhombic O phase precipitation within the D019-α2 phase has attracted increasing attention recently in high Nb containing TiAl (high Nb-TiAl) alloys since the precipitation temperature is close to the expected service temperature of the alloys. In this study, in-situ synchrotron high energy X-ray diffraction (HEXRD) reveals that the O phase precipitates at 550 °C while it dissolves into the α2 phase at 750 °C during heat treatments. However, under external stress the O phase unexpectedly precipitates from α2 phase at 800 °C and even 900 °C. The O phase formation proceeds further in the presence of a critical stress promoted by internal stress accumulation in the α2 phase, whereas the reverse O→α2 phase transformation takes place when the internal stresses are relaxed. Additionally, it has been revealed that the O phase preferentially precipitates from specifically oriented α2 grains with one of their <110> directions aligned perpendicular and their 〈0001〉 directions rotated by an angle of 120° out of the external load axis. This α2 phase orientation facilitates the α2→O crystal transition during uniaxial compression. Transmission electron microscopy (TEM) study shows that stress-induced α2→O transformation is governed by small atomic shifts in the α2 lattice. In addition, the selective growth of certain O variants via shuffling along an [110]α2 direction is found to accommodate the external strain component in this direction. KW - Titanium aluminides KW - Phase transformation KW - Strain accumulation KW - Variant selection KW - Hot compression Y1 - 2025 U6 - https://doi.org/10.1016/j.actamat.2025.120751 SN - 1359-6454 VL - 286 SP - 1 EP - 13 PB - Elsevier BV CY - Amsterdam ER - TY - GEN A1 - Stark, Andreas A1 - Rackel, Marcus W. A1 - Pyczak, Florian T1 - How rapid heating and quenching cycles affect phase evolution in advanced γ-TiAl alloys : an in situ synchrotron radiation study T2 - MRS communications N2 - Additive manufacturing (AM) processes are increasingly considered as an alternative manufacturing route to produce complex aircraft components out of γ-TiAl-based alloys. Due to the process-related high and short-time energy input, extremely fast heating and cooling rates occur which can result in thermodynamic and chemical disequilibrium. We studied the effect of rapid heating and quenching cycles in a Ti–48Al–2Nb–2Cr (in at.%) alloy by carrying out in situ high-energy X-ray diffraction experiments in which AM-related heating cycles were simulated. These in situ experiments allow to determine the influence of cooling rate and a chosen powder bed temperature on phase evolution. Y1 - 2025 U6 - https://doi.org/10.1557/s43579-025-00756-3 SN - 2159-6867 VL - 15 IS - 4 SP - 790 EP - 795 PB - Springer Science and Business Media LLC CY - Berlin ER - TY - GEN A1 - Stark, Andreas A1 - Lott, Dieter A1 - Pyczak, Florian T1 - A dilatometer and in situ synchrotron X-ray diffraction study : α-quenching and reheating of a Nb-rich titanium aluminide alloy T2 - MRS advances N2 - Intermetallic γ-TiAl-based alloys are currently used as structural materials for turbine blades in aero engines. Additive manufacturing is increasingly considered as an additional manufacturing route for components consisting of γ titanium aluminides; however, the high heating and cooling rates result in chemical and thermodynamical disequilibrated microstructures. In our study, in situ synchrotron X-ray diffraction was applied to follow the formation of the disequilibrium microstructure during quenching and to study its re-equilibration during a subsequent annealing treatment in a Nb-rich γ-TiAl-based alloy. The quenched sample showed an incomplete massive transformation, with large remaining α2 grains. During reheating, the analysis of the collected data showed that equilibration of the quenched microstructure takes place in several reordering and transformation steps, e.g., orthorhombic distortion of the hexagonal α2 phase (around 550 °C), almost complete transformation of the supersaturated quenched α2 to γ (around 850 °C), and retransformation of γ to new α2 (around 1050 °C). Y1 - 2025 U6 - https://doi.org/10.1557/s43580-025-01382-w SN - 2731-5894 VL - 10 IS - 14 SP - 1767 EP - 1772 PB - Springer Science and Business Media LLC CY - Cham ER - TY - GEN A1 - Liu, Shen A1 - Liu, Xu A1 - Wu, Qiaohan A1 - Li, Yixuan A1 - Shi, Qiuyi A1 - Song, Lin A1 - Pyczak, Florian A1 - Stark, Andreas A1 - Li, Xiaobing A1 - Zhang, Tiebang T1 - In-situ synchrotron high energy X-ray diffraction study on the internal strain evolution of an extruded Ti-45Al-8Nb-0.2C alloy during high-temperature compression T2 - Materials characterization N2 - Due to their exceptional properties, γ-TiAl based alloys present substantial prospect for aerospace and automotive applications. However, the significant disparity in plasticity between the D019-α2 and L10-γ phases greatly affects TiAl alloys' service behavior. This study investigates the internal strain accumulation in the α2 and γ phases of an extruded Ti-45Al-8Nb-0.2C alloy during compression at 900 °C and the subsequent stress relaxation behavior during annealing at 850 °C, using in situ synchrotron high-energy X-ray diffraction (HEXRD). During compression, the γ phase starts to yield plastically at approximately 410 MPa true stress, progressively shifting the load to the α2 phase and generating high residual stress in the α2 phase after deformation. However, annealing at 850 °C for 30 min only partially relieves the residual stress in the α2 phase, with the relaxation rate decreasing substantially after the first 10 min. Furthermore, when the true stress reaches 790 MPa during compression, the α2 phase undergoes rigid-body rotation to accommodate the plastic deformation of the adjacent γ phase, initiating texture evolution that ultimately forms a distinct fiber texture. KW - High Nb-TiAl alloy KW - Synchrotron radiation KW - Lattice strain KW - Stress relaxation KW - Fiber texture Y1 - 2025 U6 - https://doi.org/10.1016/j.matchar.2025.115746 SN - 1044-5803 VL - 230 SP - 1 EP - 12 PB - Elsevier BV CY - Amsterdam ER -