SUBSTRUCTURE DEVELOPMENT IN SHOCK-LOADED CU-8.7GE AND COPPER - THE ROLE OF TEMPERATURE, GRAIN-SIZE AND STACKING-FAULT ENERGY

The effect of grain size and deformation temperature on the shock-hardening response and substructure development in Cu-8. 7Ge (where the composition is in atomic per cent) has been studied, as has the behavior of copper shocked at ultrashort pulse durations. In all cases, shocking introduced deformation twins, which formeed initially as bundles of finer twins and then coalesced to form more perfect twins. Decreasing the deformation temperature did not significantly affect the shock-loading response of Cu-8. 7Ge. Increasing the grain size resulted in decreased dislocation and twin generation at short pulse durations. At long pulse durations, twin thickening dominated the deformation processes. Deformation twins were observed in copper at shock pulse durations as short as 20 ns, with the twin bundles being much thicker than those in Cu-8. 7Ge. The dislocation generation rates as a function of strain were found to be consistent with those for conventional deformation, indicating that the dislocation generation and multiplication mechanisms are the same for shock-loading and conventional deformation.