High-temperature deformation resistance and creep resistance of a TiAl-based alloy fabricated by cold crucible direction
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https://doi.org/10.1007/s41230-020-0088-1
High-temperature deformation resistance and creep resistance of a TiAl-based alloy fabricated by cold crucible directional solidification technology Shu-lin Dong1,2, Xin Ding2, *Rui-run Chen2, Jing-jie Guo2, Heng-zhi Fu2 1. Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819, China 2. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
Abstract: In order to improve the high-temperature deformation resistance and creep resistance of TiAl-based alloys, cold crucible directional solidification (CCDS) technology was employed. A β-type TiAl-based alloy with the nominal composition of Ti44Al6Nb1Cr2V was prepared using the optimized CCDS parameters of 45 kW input power and 0.5 mm·min-1 solidification rate. Thermo-compression testing was utilized to evaluate the hightemperature deformation resistance and creep resistance of the CCDS Ti44Al6Nb1Cr2V alloy. Results show that the CCDS Ti44Al6Nb1Cr2V alloy billets contain aligned columnar grains and a high percentage of small-angle lamellae. Thermo-compression testing results in the radial direction of the CCDS alloy show a much higher peak stress than other reported results in similar conditions. The much higher hardening exponent and deformation activation energy are obtained, corresponding to the excellent high-temperature deformation resistance and creep resistance, which are because of the hard-oriented grains, weaker stress-strain coordination capability of lamella structure and relatively more hysteretic dynamic recrystallization. Thermo-compression testing results in the longitudinal direction of the CCDS Ti44Al6Nb1Cr2V alloy show the much higher peak stress than that in the radial direction, indicating the better high-temperature deformation resistance and creep resistance attributed to the hard-oriented lamellae in this condition. Key words: cold crucible directional solidification; TiAl; thermo-compression; constitutive equations; microstructure CLC numbers: TG146.23
Document code: A
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iAl-based alloys have wide application prospect in the aerospace field due to their low density, high strength and high service temperature [1-2]. As the potential high-temperature structural materials, the higher high-temperature deformation resistance and creep resistance are of importance [3-5], which are directly related with the service capability and service life of workpieces. Cold crucible directional solidification (CCDS) technology is an excellent fabrication method to improve the high-temperature deformation resistance and creep resistance of TiAl-based alloys [6-7], since the aligned columnar grains and aligned (α 2+γ) lamellae can be obtained by using this method. The aligned columnar grains can be easily obtained by CCDS, because stable and sufficient power can be supplied for the directional growth of grains during directional solidification [8, 9]. *Rui-run Chen Male, Ph.D., Professor. Research interests: hi
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