Temperature effects on the mechanical behavior of ultrafine-grained material

The quasi-static and dynamic compression experiments of ultrafine-grained copper fabricated by equal channel angular pressing method were performed at temperatures ranging from 77 to 573K. The influence of temperature on flow stress, strain hardening rate and strain rate sensitivity were investigated. The results show that the flow stress of ultrafine-grained copper shows much larger sensitivity to testing temperature than that of coarse grained copper. However, the temperature sensitivity of ultrafine-grained copper to true strain is comparative weaker than that of coarse grained copper. For the ultrafine-grained copper, both the strain hardening rate and its sensitivity to temperature of ultrafine-grained copper are lower than those of its coarse counterpart. The SRS also displays apparent dependence on temperature. The activation volume for UFG-Cu is estimated to be on the order of ∼10b³ in current experiment temperature. It is suggested that the dislocation-grain boundary interactions process might be the dominant thermally activated mechanism for UFG-Cu.