On the shape of edge-dislocation loops in βNiAl

Abstract

The shapes of edge dislocation loops in β-NiAl have been studied. These loops have {001} habit planes, 〈001〉 Burgers vectors and exhibit two distinct forms. One of these is roughly square with segments nearly parallel to 〈010〉; this corresponds to the equilibrium shape calculated on the basis of elastic anisotropy. The other form consists of segments aligned accurately parallel to 〈110〉, which should be elastically unstable. It is proposed that this second shape is stabilized by dissociation of the perfect dislocation into three partial dislocations on the intersecting {110} planes for example

The consequences of such a dissociation for the plastic deformation of β-NiAl are discussed.