The behaviour of copper-12% aluminium under simple reversed stresses

Abstract

Experiments are described in which slip steps on Cu-12.5 at.% Al have been studied using a recently developed replica technique that enables small changes in the heights of slip steps to be accurately located and determined. Slip steps which formed during a tensile prestrain are shown to have become smaller after a subsequent compressive strain. This is interpreted as the reverse movement, during compression, of dislocations which were generated during the prestrain. The density of slip lines, which undergo reverse slip, is a function of strain and this is shown to have a maximum at the end of stage 1. It is further shown that reverse slipping dislocations are responsible for the Bauschinger effect. Data are presented to show that the ageing time of the alloy has a definite effect on the magnitude of the Bauschinger strain.