Some features of the formation and destruction of dislocation barriers in intermetallic compounds: II. Observation of blocked superidislocations upon heating without stress

Abstract

Experiments have been performed which reveal that heating in the absence of an external stress after a preliminary both low-temperature and high-temperature deformation of intermetallic compounds leads to a fundamental change in their dislocation structure. For the investigation, [251] single crystals of Ni₃(Al, Nb) have been used. The low-temperature deformation was performed at −196°C; the high-temperature deformation, at 800°C. It has been found that the initial dislocation structure consisting of curvilinear dislocations was changed upon heating without a load by a set of rectilinear blocked dislocations. It has been shown that upon heating after a preliminary low-temperature deformation the barriers present in the structure belong to the cubic cross-slip plane, whereas upon heating after high-temperature deformation, to primary cubic slip planes. It has been found that the decisive effect on the blocking of superdislocations upon heating without stress comes from one of the dislocations that compose the superdislocation, namely, either a superpartial dislocation in the case of low-temperature deformation or a simple partial dislocation in the case of high-temperature deformation. The concept of the possibility of thermoactivated blocking of superdislocations in the absence of external stresses suggested in part I of this work [Phys. Met. Metallogr. 102, 61–68 (2006)] has been confirmed experimentally.