Producing of Fatigue Cracks and Fracture in Ultrafine-grained High Performance Cu-0.6Cr Copper Alloy
The producing of fatigue cracks and fracture in the ultrafine-grained(UFG) and coarse grained(CG) Cu-0.6Cr copper alloy prepared by equal channel angular pressing were studied.The surface and fracture surface images of UFG and CG were observed by means of scanning electron microscopy.The results show that the persistent slip bands of CG Cu-0.6Cr copper alloy is mixed up,the shear bands of UFG Cu-0.6Cr copper alloy developing along the shear planes of the last ECAP process are decisive for fatigue crack initiation and early crack propagation.The share plane of extrusion deformation and the slipping along the grain boundary of plane interface is the mostly forming mechanism of shear bands during cyclic deformation.The fracture of CG Cu-0.6Cr copper alloy is plastic fracture,but the fracture of the UFG Cu-0.6Cr copper alloy shows the brittle properties.