Fatigue Property and Fatigue Cracks of Ultra-fine Grained Copper Processed by Equal-channel Angular Pressing

摘要

The fatigue life, cyclic deformation behavior and microstructure of ultra-fine grained (UFG) copper produced by equal-channel angular pressing (ECAP) were tested and observed in present work. Development of surface relief and fracture surfaces were observed by means of scanning electron microscopy. The results show that the higher tensile strength UFG copper has lower ductility and its strain controlled cyclic properties are worse while comparing with those of lower strength CG counterpart. All the ECAP specimens display obvious cyclic softening behavior under the applied strain range. The cyclic softening ratio increases with increasing strain amplitude. The cyclic hysteresis loops of UFG Cu shows the tension and compression peak stresses decreased gradually with number of cycles. The formation of SBs and grain boundary sliding is the main factor causing crack nucleation as well as premature failure.