The influence of strain rate on the mechanical properties and dislocation substructure in deformed copper single crystals

Abstract

The mechanical properties, dislocation configurations and densities have been investigated in single crystals of copper deformed in the strain-rate range 10⁻⁴ to 10⁴ sec⁻¹. It was found that the flow stress of copper exhibits two regions of strain-rate sensitivity. Below strain rates of 10³ sec⁻¹ the flow stress was relatively insensitive to strain rate but above 10³ sec⁻¹ the flow stress is a sensitive linear function of the strain rate. However, the dislocation density and configurations versus strain were found to be almost independent of strain rate throughout the range 10⁻⁴ to 10⁴ sec⁻¹. There was a straight line relationship between the flow stress and the square root of the dislocation density at all strain rates. However, at a strain rate of 6·5 X 10³ sec⁻¹ there is a positive intercept τ₀ on the stress axis at zero dislocation density. The term τ₀ can be related to the damping process retarding dislocation motion.