Temperature‐Dependent Microstructures in Fatigued Ultrafine‐Grained Copper Produced by Equal Channel Angular Pressing

Ultrafine‐grained copper samples produced by equal channel angular pressing were cyclically deformed at different temperatures under a constant stress amplitude of 200 MPa, and the corresponding microstructures were investigated by transmission electron microscope. The increase in temperature during cycling facilitated the grain coarsening and led further to the general change of microstructures from dislocation walls to well‐defined cells as well as to the occurrence of a few annealing twins in final microstructures of fatigued UFG copper at the temperature above recrystallization.