Role of recovery in high temperature constant strain rate deformation

Abstract

A model based on the three-dimensional distribution of dislocations is used to delineate the role of recovery during high temperature constant strain rate deformation. The model provides a good semi-quantitative explanation for classical work-hardening as well as for high temperature work-softening resulting from rapid recovery. It predicts linear work-hardening, whereby the ratio of the work-hardening rate,H, to the shear modulus,G, is constant when a crystal is tested in the absence of recovery. The slope of the stress-strain curve, θ, for high temperature deformation is related to the low temperature work-hardening rateH; the dislocation annihilation rate\(\dot \rho _a \), the flow stress a, the free dislocation density ρ, the strain rate\(\dot \varepsilon \), and a parameter which is sensitive to the dislocation distribution. A modified version of the Bailey-Orowan equation for simultaneous work-hardening and recovery during constant strain rate deformation which is derived from the model takes the form $$\theta = H - \eta (t)R/\dot \varepsilon $$ whereR is the rate of recovery and η(t) which is time-dependent during the transient stage of deformation, is determined by such factors as σ, ρ and the details of the dislocation distribution.