Stress transients at changes of electron drag during plastic deformation of metals

Abstract

At low temperatures, the electronic state of a metal may influence its plastic deformation behavior. Many experiments show a pronounced decrease in the flow stress when superconductors enter the superconductive state. More recently stress changes in normal state metals were observed when the applied magnetic field was changed. The theory of Suenaga and Galligan and Granato explains these observations in terms of a dislocation inertial effect. In this theory the damping of dislocations between obstacles is taken to be very small and the mobile dislocations overshoot their static equilibrium position. According to this theory the dynamic interaction of a dislocation and a pinning point leads to a change in the effective instantaneous stress τ*, τ*≈τ(2-BL/2√AC) (1) where B is the viscosity coefficient, C the dislocation line tension, A the effective dislocation mass per unit length, and L the distance between pinning points. We note that only if the assumption, BL << 2√AC is valid, should an effect be observable.