Effect of cooling rate on transformation texture and variant selection during β → α transformation in Ti–5Ta–1.8Nb alloy

The evolution of texture in a cold rolled Ti–5Ta–1.8Nb alloy sheet, during the α → β → α transformation has been studied using EBSD and XRD techniques, for different cooling rates. The sheet exhibited a basal plane type texture upon cold rolling, and a sharp ‘{1 1 −2 0}||rolling plane’ transformation texture was inherited after the heat treatment. The microtexture analysis of the lamellar α/β structure, suggested that this transformation texture arises from the {1 1 1}〈1 1 0〉 type of high temperature β texture, obeying the Burgers orientation relationship. The strength of the transformation texture was found to sharply increase with decrease in cooling rates, denoting variant selection. Two types of parent β orientations with [1 1 0] parallel to either rolling directions are possible, and among their α product variants, 3 of them are common, and can be preferentially formed at the prior-β grain boundaries. The role of grain boundary-α in influencing variant selection and the transformation texture for different cooling rates is described in this paper.