The effect of temperature on mechanical behavior of ultrafine-grained copper by equal channel angular pressing

Quasi-static compression experiments of annealed coarse grained copper (Cu 99.9) and ultrafine-grained copper fabricated by equal channel angular pressing method were performed at temperatures ranging from 77 to 573K. Based on experimental results, the influence of temperature on flow stress, strain hardening rate is investigated carefully. The results show that the flow stress of ultrafine-grained copper displays much larger sensitivity to testing temperature than that of coarse grained copper. However, the temperature sensitivity of ultrafine-grained copper to true strain is comparatively weaker than that of coarse grained copper. Moreover, for the ultrafine-grained copper, both the strain hardening rate and its sensitivity to temperature are lower than those of its coarse counterpart. Based on thermal activation theory, it is proposed that the enhanced temperature sensitivity of ultrafine-grained copper can be related to the reduction in activation volume due to grain refinement.