Experimental studies were conducted on the tensile behaviors and fracture modes of TiAl (Ti-46.5Al-2Nb-2Cr) alloys with near gamma (NG) equiaxed and near lamellar (NL) microstructures over a temperature range from room temperature to 840 ℃ and a strain rate range of 0.001-1 350 s-1. The results indicate that the alloys are both temperature and strain rate dependent and they have a similar dependence. The dynamic strength is higher than the quasi-static strength but almost insensitive to high strain rate range of 320-1 350 s-1. The brittle-to-ductile transition temperature (BDTT) increases with increasing strain rates. NG TiAl yields obviously, while NL TiAl does not. Below BDTT, as the temperature increases, the fracture modes of the two alloys change from planar cleavage fracture to a mixture of transgranular and intergranular fractures, and finally to totally intergranular fracture.%研究Gamma等轴NG组织和近片层NL组织的Ti-46.5Al-2Nb-2Cr合金在不同温度和应变率下的力学行为和断裂模式,揭示温度和应变率对不同微观组织的力学行为和断裂特性的影响.结果表明,两种微观组织的TiAl合金均与温度和应变率相关,且具有类似的温度和应变相关性:动载下的强度明显高于静载下的强度,但在高应变率范围内(320-1 350 s-1)无明显的应变率相关性;韧脆转变温度(BDTT)随应变率的增加而升高;等轴组织的TiAl合金的真应力-真应变曲线中可以看到明显的屈服现象,而近片层组织的屈服现象不明显.在韧脆转变温度以下,随着温度的上升,两种组织的TiAl的断裂方式均由穿晶解理断裂转变为穿晶断裂与沿晶断裂的混和模式,最后转变为沿晶断裂方式.
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