Dislocation-Induced Dispersion of Nanoparticles As a Reason for the Cyclic Functional Instability of Ni–Fe–Ga–Co Alloys

Abstract

A physical mechanism underlying the cyclic functional instability of as-grown Ni₄₉Fe₁₈Ga₂₇Co₆ alloy crystals has been discussed in terms of the theory of diffuse martensitic transitions. The crystals have been subjected to “compression along the [011] direction–shape memory strain recovery by heating” thermomechanical cycles. Cycling causes a considerable reduction of compression stresses and their stabilization after nine to ten thermomechanical cycles. It has been analytically shown that the reduction of compression stresses is associated with the dispersion (disordering) of antiphase domains by slip dislocations. As a result, the antiphase nanodomain B₂ superstructure of the as-grown crystal transforms into the L2₁ structure characteristic of the given alloy subjected to high-temperature postgrowth annealing.