TY - GEN A1 - Song, Lin A1 - Hu, Xingguo A1 - Wang, Li A1 - Stark, Andreas A1 - Lazurenko, Daria V. A1 - Lorenz, Uwe A1 - Lin, Junpin A1 - Pyczak, Florian A1 - Zhang, Tiebang T1 - Microstructure evolution and enhanced creep property of a high Nb containing TiAl alloy with carbon addition T2 - Journal of Alloys and Compounds Y1 - 2019 U6 - https://doi.org/10.1016/j.jallcom.2019.151649 SN - 0925-8388 VL - 807 ER - TY - GEN A1 - Song, Lin A1 - Wang, Li A1 - Zhang, Tiebang A1 - Lin, Junpin A1 - Pyczak, Florian T1 - Microstructure and phase transformations of omega_o-Ti4Al3Nb based alloys after quenching and subsequent aging at intermediate temperatures T2 - Journal of Alloys and Compounds Y1 - 2020 SN - 0925-8388 VL - 821 ER - TY - GEN A1 - Song, Lin A1 - Appel, Fritz A1 - Wang, Li A1 - Oehring, Michael A1 - Hu, Xingguo A1 - Stark, Andreas A1 - He, Junyang A1 - Lorenz, Uwe A1 - Zhang, Tiebang A1 - Lin, Junpin A1 - Pyczak, Florian T1 - New insights into high-temperature deformation and phase transformation mechanisms of lamellar structures in high Nb-containing TiAl alloys T2 - Acta Materialia Y1 - 2020 U6 - https://doi.org/10.1016/j.actamat.2020.01.021 SN - 1873-2453 SN - 1359-6454 VL - 186 SP - 575 EP - 586 ER - TY - GEN A1 - Liu, Xu A1 - Song, Lin A1 - Stark, Andreas A1 - Lorenz, Uwe A1 - He, Zhanbing A1 - Lin, Junpin A1 - Pyczak, Florian A1 - Zhang, Tiebang T1 - Deformation and phase transformation behaviors of a high Nb-containing TiAl alloy compressed at intermediate temperatures T2 - Journal of Materials Science and Technology N2 - In modern β-solidified TiAl alloys, the decomposition of α2 phase is frequently observed during heat treatment or high-temperature deformation of the alloys. In this study, high-temperature deformation and decomposition mechanisms of α2 phase in a Ti-45Al-8.5Nb-0.2B-0.2W-0.02Y alloy are investigated. In a sample deformed at 800 °C, the precipitation of βo(ωo) phase is observed within the equiaxed α2 phase. The nucleation of ωo particles within the βo matrix indicates the α2→βo→ωo transformation. In addition, numerous γ phase precipitates form within the βo(ω) areas. The α2 lamellae decompose into ultrafine (α2+γ) lamellae and coarsened γ lamellae via α2→α2+γ and α2→γ transformation, respectively. Moreover, the ωo phase nucleates within the ultrafine lamellae via α2→ωo transformation. However, in a sample deformed at 1000 °C, the nucleation of βo particles is sluggish, which is caused by the efficient release of the internal stress via dynamic recrystallization (DRX). These results indicate that complex phase transformations can be introduced by the decomposition of α2 phase in TiAl alloys with a high amount of β-stabilizing elements. Y1 - 2022 U6 - https://doi.org/10.1016/j.jmst.2021.06.041 SN - 0861-9786 VL - 102 SP - 89 EP - 96 ER - TY - GEN A1 - Song, Lin A1 - Appel, Fritz A1 - Pyczak, Florian A1 - Zhanbing, He A1 - Junpin, Lin A1 - Tiebang, Zhang T1 - Characterization of primary, secondary and tertiary {202¯1}<1¯014> successive internal twins in the D019 ordered hexagonal α2-Ti3Al phase T2 - Acta Materialia N2 - Due to the lack of independent slip systems and the difficulty in mechanical twinning, D019 ordered α2-Ti3Al phase is known to be of substantial mechanical anisotropy, which partly accounts for the low ductility of two-phase (α2+γ) TiAl alloys. However, recent studies have shown that in Al-rich α2 phase compression deformation twins can be activated, which could be beneficial for the ductility of the alloys. In the present study, for the first time, we have revealed a novel internal twinning mechanism of α2 phase in a TiAl alloy deformed at high temperature. Three twin generations of a common type {202¯1}[removed] were revealed: Secondary twins formed within the primary twin, and tertiary twins formed in the secondary twin. It is important to note that this internal twin structure can only be observed in the [removed] direction but not the commonly used [removed] direction. The shear plane P of all twin variants is of type {12¯10}. Due to the variation of the twinning elements between the twin variants, the twinning shear is blunted. The interfaces between the twin variants are characterized by high-resolution electron microscopy. Special attention was paid to the structure of the coherent and incoherent twin boundaries. The effect of chemical ordering is discussed. Our results also shed light on the complex twinning mechanisms in hexagonal structures. Y1 - 2022 U6 - https://doi.org/10.1016/j.actamat.2021.117391 SN - 1873-2453 IS - 222 ER - 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 - 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 - Song, Lin A1 - Appel, Fritz A1 - Liu, Wenhao A1 - Pyczak, Florian A1 - Zhang, Tiebang T1 - {11¯01} tension twins and {11¯01}-{22¯01}/{22¯01}-{11¯01} double twins in the D019 ordered hexagonal α2-Ti3Al phase T2 - Acta Materialia Y1 - 2023 U6 - https://doi.org/10.1016/j.actamat.2023.119335 VL - 260 IS - 3 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 - 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 -