Superplasticity of a γ-TiAl alloy and its microstructure and cavity evolution in deformation

A fine-grained γ-TiAl based alloy was synthesized by Pulse Current Auxiliary Sintering. Tensile properties of the sintered alloy were investigated at temperatures ranging from 800 °C to 1000 °C. Results showed that the alloy under study displayed superplasticity at temperatures of over 900 °C, and the activation energy Q for its superplastic deformation was determined as 212.6–252.2 kJ mol−1, corresponding to the deformation mechanism of grain boundary sliding accommodated by grain boundary diffusion. Additionally, it was also found that in superplastic deformation, microstructure and cavity evolution took place, such as axial elongation or growing of γ, breaking up of α2, nucleating and growing of cavities in the vicinity of big α2 grains. All the observed phenomena are tried to be explained in the paper.