The plastic properties of high-purity W single crystals

Abstract

Two tests of high-purity W single crystal oriented for single slip were performed by deformation in tension at constant plastic strain rate in the temperature range of 26–800 K. One test consisted in an isothermal deformation of the specimens up to their ultimate tensile strain at several temperatures (type-A tests). Another test consisted in successively deforming a sample in small strain intervals at different (decreasing) temperatures (type-B tests) after a first deformation at ≥600 K. Tests were combined with stress–relaxation experiments to determine the strain-rate sensitivity of a relevant shear stress. Type-A tests exhibit a parabolic shape of the work-hardening curves with a rather high work-hardening rate at the beginning, which decreases continuously thereafter. In contrast to this behaviour, the short stress–strain curves within the short strain intervals of type-B test show no work hardening, but a plateau after yielding.