Dynamic behavior and fracture mode of TiAl intermetallics with different microstructures at elevated temperatures

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 °C 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.