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

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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.