Propagation of stacking faults across domain boundaries in Ni-V and Ni-V-Nb alloys with D0[sub 22] structure.

Disorder-to-order reaction in stoichiometric Ni[sub 3]V and Ni[sub 75]V[sub 21.5]Nb[sub 3.5] alloys involve a cubic (fcc)-to-tetragonal (D0[sub 22] structure) transformation. The structural changes occurring during the transformation result in a lamellar morphology of D0[sub 22] domains with {110}[sub fcc]-type interfaces. The propagation of stacking faults across domain boundaries in Ni[sub 3]V and Ni[sub 75]V[sub 21.5]Nb[sub 3.5] has been studied using transmission electron microscopy. Different modes of propagation of stacking faults across these boundaries have been observed. These modes have been attributed to the generation of appropriate glide partials at the domain boundaries. The nature and the Burgers vectors of the glide partials have been identified using visibility and invisibility criteria. Computer simulation results have been used to substantiate the results of contrast experiments. Dislocation reaction mechanisms responsible for the generation of these glide partials have been identified. In the present work, special emphasis has been laid on the propagation mode by which stacking faults cross the domain boundaries in the same glide plane. [ABSTRACT FROM AUTHOR]