The annihilation of superdislocations in Ni₃Al during deformation at room temperature

Abstract

Transmission electron microscopy evidence is given of mechanisms. of annihilation that take place in the course of the room-temperature plastic deformation of Ni₃Al. Under a load orientation that favours the operation of a single-slip system, the short dipoles that are present in foils sectioned parallel to the slip plane are identified as elongated closed superdislocation loops instead of dipoles terminating at free surfaces. The fact that dipoles are often aligned in rows such that one extremity of a given dipole corresponds with the closest extremity of the next dipole in the screw orientation is explained in terms of the cross-slip properties of Ni₃Al-based alloys. The presence of two distinct categories of dipole rows is interpreted in terms of two different approach mechanisms. The formation of antiphase-boundary tubes-by direct annihilation of screw segments is questioned.