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 phase (α), and the original α/β interface in the bimodal microstructure largely disappears, forming a blurry interface between the semi-equiaxed α phase (equiaxed α phase that is grew through by the thin β lamellae) and the transformed β microstructure (β). The formation of dense slip bands inside the semi-equiaxed α 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/β interface decreased compared to the distinct α/β 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.