Yield-Point Behaviour in Cu–1 at.-% In Single Crystals

Abstract

Deformation characteristics of Cu–1 at.-% In single crystals are presented for a range of orientations at temperatures from 77 to 473 K. Macroscopic slip commences with a yield point followed by a Lüders strain. The shear during the Lüders strain is markedly orientation-dependent and increases with decreasing temperature. Subsequent to the Lüders strain, work-hardening Stages I and II are seen in nearly all cases. Stage II is followed by a stage of conjugate slip which often begins with an inhomogeneous propagation. Subsequent to this propagation, or in its absence, hardening on the conjugate system proceeds in a linear fashion at a rate of between 3 and 7 kgf/mm² (29 and 69 MN/m²), dependent on orientation. The inter-relationship of Lüders strain and hardening rate during Stage I is discussed in detail. Models of the yield point, based on dislocation multiplication effects, account fairly well for the observed orientation-dependence of Lüders strain at 293 K, but modifications are necessary to explain the temperature-dependence of the Lüders strain.