Deformation Behavior and Tensile Properties of the Semi-Equiaxed Microstructure in Near Alpha Titanium Alloy

The tensile deformation and fracture behavior of a particular semi-equiaxed microstructure (S-EM) in a near alpha titanium alloy TA19 are investigated by an in situ method. In the S-EM, the thin β lamellae grow through the equiaxed α(p) phase (α(p)), and the original α(p)/β(trans) interface in the bimodal microstructure largely disappears, forming a blurry interface between the semi-equiaxed α(p) phase (equiaxed α(p) phase that is grew through by the thin β lamellae) and the transformed β microstructure (β(trans)). The formation of dense slip bands inside the semi-equiaxed α(p) phase in the S-EM is inhibited by the thin β lamellae during the tensile deformation. The special characteristics of the S-EM reduce the stress concentration at the interface, and the crack initiation probability in the blurry semi-α(p)/β(trans) interface decreased compared to the distinct α(p)/β(trans) interface in a conventional equiaxed microstructure (EM). Moreover, the ultimate tensile strength of the S-EM is higher than that of the EM with a slight loss of plasticity.