The plastic properties of high-purity W single crystals

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 greater than or equal to 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. Zn 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. (C) 2000 Elsevier Science B.V. All rights reserved.