Creep and stress relaxation studies with polycrystalline magnesium

Abstract

The temperature and stress dependence of the secondary creep rate of fine-grained polycrystalline magnesium have been investigated in the strainrate range 3·3 × 10⁻¹ to 3·3 × 10⁻³ sec⁻¹. Stress relaxation studies were combined with the creep experiments to obtain accurate values for the activation volume. They also gave evidence of long-range internal stresses. Results have been interpreted according to a model of thermally activated screw dislocation glide in which intersection jogs determine the activation volume and probably the glide-rate also. Additional experiments for creep rates less than 10⁻⁴ sec⁻¹ indicated that in this range the recovery of athermal obstacles is rate-determining.