Pseudo-Twinning in A Deformed Nb-15Al-25Ti B2 Alloy

Abstract

AbstractAn alloy with nominal composition of Nb-15Al-25Ti (in at.%) has been developed for high temperature structural applications. This alloy exhibits a B2 ordered structure in the as-cast form [1]. In addition to dislocation slip, pseudo-twinning occurs in this B2 alloy when deformed in compression at room temperature at a strain rate of ∼ 10−4 sec−1 to 3% strain. The pseudo-twinning plane has been deduced to be the {112} planes, which is similar to that in twinning of bcc metals. The mechanism of deformation pseudo-twinning in this B2 alloy is found to be analogous to the normal twinning mechanism in bcc metals, involving glide of partial dislocations with Burgers vector (b) given by b=l/6<111= on {112} planes. This pseudo-twinning mechanism causes a phase transformation from the B2 to an ordered orthorhombic structure.