TEM investigation of dislocation dissociation in L1₂-type Co₇₄Ni₃Ti₂₃ single crystals I. The effect of applied stress

Abstract

Transmission electron microscopy in situ weak-beam investigations have been made on superdislocation cores in Co₇₄Ni₃Ti₂₃ single crystals deformed at room temperature. Contrast experiments using [220] reflections show that a core transition of superdislocations from superlattice intrinsic stacking fault dissociation into antiphase boundary dissociations occurs under the applied stress. This process is shown to be reversible by applying and removing the external stress. The peculiar temperature and orientation dependence of the critical resolved shear stress observed at low temperatures can be explained on the basis of the core transition process.