Slip-plane disordering in stoichiometric Ni3Al

Abstract

Observations during in situ straining experiments on stoichiometric Ni₃Al in a transmission electron microscope are presented showing that a non-conservative loop generation mechanism operates in highly-deformed slip bands. Apparently, after passage of many superlattice dislocations the antiphase boundary energy (APB) in the slip band is lowered, superpartial separations increase, and some defects (such as vacancy and anti-site) coalesce and aid the formation of the loops. These observations correlate well with recent suggestions that non-planar APBs are present and can glide. Similar experiments in alloys that do not order do not produce such loops. These loops serve as pinning points to passage of subsequent dislocations. The separations of superpartial dislocations measured under load are greater than those measured in bulk deformed but unloaded specimens.