面心立方晶の加工硬化曲線における段階IからくIIへの遷移機構

Abstract

The transition from stage I to II in the deformation of Cu, Cu-1 at%Ge, and Ag single crystals has experimentally been studied with particular attention to the formation of deformation bands (kink bands) through ‘bend gliding’. The bend gliding originates from the local inhomogeneity of primary main slip in a specimen deformed under the uniaxial tension, and the slip inhomogeneity is enhanced by the presence of grown-in sub-boundaries. It is shown that stage I terminates with the formation of kink bands through the stabilization process of the local bend-gliding regions. At the kink-band boundary dislocations are blocked from further movement and rapidly accumulated. Consequently the flow stress is increased and also secondary slip systems are activated by the stress concentration, resulting in a swift transition from stage I to II. The temperature dependence of the extent of stage I, which has generally been observed but not well understood, can also be interpreted in terms of the formation of dislocation walls or kink bands which becomes easier as the deformation temperature is raised. In this connection, a phenomenon named ‘annealing-hardening in pure metals’ found in stage I may provide evidence in support of this view.