On the formation mechanism of faulted dipolar loops in gamma -TiAl

Abstract

] Some new geometrical features of 1/6<112] faulted dipolar loops have been observed in a Ti-52 at.% Al alloy deformed at 77 K. It was observed that the 1/6<112] dipole could switch its alignment from <101] to <011] directions, and vice versa; also the loops in alignment along both <101] and <011] could be created by the same parent superdislocation along its line and, on further movement of the parent dislocation, the two loops could attach to one another at the meeting point. No extra dislocation debris or segments were created at either the turning point or the attachment site. These particular features have been discussed on the basis of the available models for the formation mechanism of the dipoles. It is predicted that the particular features can be created only under a favourable stress and no such features are expected for 1/3<211]faulted dipolar loops.