Experimental investigation on strain rate sensitivity of ultra-fine grained copper at elevated temperatures

Quasi-static and dynamic compression tests on ultra-fine grained (UFG) copper (Cu 99.9) were performed at temperatures ranging from 77 to 573 K and strain rates ranging from 10^-3 to 5 × 10³ 1/s using an electronic universal testing machine and the split Hopkinson pressure bar system, respectively. We focused on the strain rate sensitivity and its dependence on experimental temperatures. The results show that UFG-Cu has enhanced strain rate sensitivity that is apparently temperature dependent. The activation volume of UFG-Cu is estimated to be on the order of ∼10b ³ at current experimental temperature and strain rate range. The plastic deformation mechanism is suggested to be dislocation-grain boundary interactions.