Discontinuous yielding and microstructural evolution of Ti-40 at.% Al alloy compressed in single α-hcp phase region

Abstract We examined the hot deformation behaviors of Ti-40 at.% Al alloy via hot compression tests at temperatures in the range of 1423–1523 K (single α-hcp phase) at strain rates in the range of 1–0.001 s−1. Specifically, we investigated the discontinuous yielding phenomenon and the strain rate dependence of the microstructural evolution of the alloy. Sharp drops in flow stresses occurred during hot compression at strain rates of 1 s−1 and 0.1 s−1, which were attributed mainly to both the multiplication of dislocations and the formation of deformation twins. The twins were determined as being of the compound type with the following twin elements: K1: { 11 2 ¯ 1 } , K2: { 11 2 ¯ 2 ¯ } , η1: 11 2 ¯ 6 ¯ > , η2: 11 2 ¯ 3 > , s = 0.232. The grains of the α2-Ti3Al single phase were more significantly refined and homogenized by hot compression at a high strain rate of 1 s−1 than at a low strain rate of 0.001 s−1, with the assistance of the deformation twins at the high strain rate.