Wu Qianqian, Cui Ning, Xiao Xiaohong, Wang Xiaopeng, Zhao Ertuan
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao 266520, China.
State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China.
Materials (Basel). 2019 Jul 6;12(13):2172. doi: 10.3390/ma12132172.
In this paper, the hot deformability and mechanical properties of a novel Mn- and Nb- containing TiAl alloy were studied systematically with the use of isothermal compression experiments. The results show that the alloy has low deformation resistance and a low activation energy (392 KJ/mol), suggesting that the alloy has good hot deformability. A processing map was established, which shows that the present alloy has a smaller instability region and wider hot working window compared with other TiAl alloys. Microstructural observation shows that the initial lamellae completely transformed into fine equiaxial γ grains when the alloy was compressed at 1200 °C/0.01 s, which corresponds to the optimum deformation condition. Based on the above results, an intact TiAl billet was successfully fabricated by one-step large deformation using a four-column hydraulic machine. The microstructure of the billet is almost completely composed of recrystallized γ grains with large angle boundaries. Tensile testing shows the billet exhibits high tensile strength (780 MPa) and high elongation (1.44%) simultaneously, which benefits from fine γ grains with an average size of 4.9 μm. The ductile-brittle transition temperature is between 750-800 °C.
本文通过等温压缩实验系统研究了一种新型含锰和铌的TiAl合金的热变形性和力学性能。结果表明，该合金具有较低的变形抗力和较低的激活能（392 kJ/mol），表明该合金具有良好的热变形性。建立了加工图，结果表明，与其他TiAl合金相比，该合金的失稳区域更小，热加工窗口更宽。微观组织观察表明，当合金在1200℃/0.01 s条件下压缩时，初始片层完全转变为细小等轴γ晶粒，这对应于最佳变形条件。基于上述结果，使用四柱液压机通过一步大变形成功制备了完整的TiAl坯料。坯料的微观组织几乎完全由具有大角度晶界的再结晶γ晶粒组成。拉伸试验表明，坯料同时具有高拉伸强度（780 MPa）和高伸长率（1.44%），这得益于平均尺寸为4.9μm的细小γ晶粒。韧脆转变温度在750 - 800℃之间。
