INFLUENCE OF STRAIN RATE ON 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. © 1969 Taylor & Francis Group, LLC.