The Formation of Crystallographically Aligned a/3 <112> Dislocations in Ni3Al

Abstract

Although intrinsic stacking faults have been observed in cold rolled polycrystalline Ni3Al, the terminating superlattice partial dislocations have not been identified. Since superlattice intrinsic stacking faults (S-ISF) can be formed by the glide of a/3 <112> partials, we have recently suggested specific interactions between paired a/2 <110> slip dislocations which could result in the formation of such partials. In the present study the partial dislocations and associated stacking faults formed during multiple slip in Ni3Al are identified. These partials have a/3 <112> Burgers vectors and lie parallel to <110> directions. The latter is explained in terms of the relaxation of the superlattice partials along cube planes.Thin foils were prepared from sheets of directionally solidified columnar-grained Ni3Al that had been rolled (~ 5% reduction) along the common <100> direction. While the familiar long straight a/2 <110> type screw dislocation pairs were observed in some grains, extended stacking faults were present in most areas of the foil where multiple slip had occurred, Figure 1.