Effect of temperature on the flow stress and strain-hardening coefficient of magnesium single crystals

Abstract

The initial yield stress and plastic flow characteristics of magnesium single crystals have been investigated by means of incremental creep experiments in tension and direct shear, in the temperature range of 78° to 364°K. It was found that the strain rate, γ̇, could be related to the applied stress, τ, and the temperature, T, by the expression $C\exp \left(-\frac{\Delta H}{kT}\right)\exp B(\tau -h\gamma )$, where B and C are constants, h is the strain-hardening coefficient, γ is the strain, and ΔH is an activation energy equal to 10.3 kcal per g atom. The strain-hardening coefficient was constant in the temperature range of 78° to 203°K, but decreased at higher temperatures; the decrease is attributable to recovery. The constant coefficient, in the absence of recovery, is consistent with the idea that strain hardening in hexagonal crystals is associated with the elastic interaction of accumulated dislocations.