Effect of varying a phase fraction on the mechanical properties and deformation mechanisms in a metastable β-ZrTiAlV alloy

We systematically investigated the effects of varying a phase fraction on the mechanical properties and deformation mechanisms in a metastable beta-51.1Zr-40.211-4.5A1-4.2V (wt. %) alloy containing mixed alpha + beta phase. Various heat treatments from single beta phase regime to dual alpha+beta phase regime were imposed in order to alter the volume fraction of alpha phase. The results show that the triggering stress increases and the total elongation decreases with the increasing a phase fraction. As the alpha phase fraction increases, the work hardening rate curve changes from an obvious parabolic evolution to a monotonically decreasing evolution and the work hardening effect is gradually reduced. Co-existence deformation mechanisms of kink bands, deformation-induced alpha' martensite and {10 (1) over bar1}(alpha') mechanical twinning were detected in low alpha phase fraction samples but not in high alpha phase fraction sample. In intermediate alpha phase fraction sample, only deformation-induced alpha' martensite was activated. For the first time, the effects of a phase fraction on the deformation-induced alpha' martensite, {10 (1) over bar1}(alpha') mechanical twinning and kink bands were observed in metastable beta-Zr alloy. These effects of varying a phase fraction on the mechanical properties and deformation mechanisms are discussed based on the beta stability and the fi domain size.