Fracture Behavior of Annealed and Equal Channel Angular Pressed Copper: An Experimental Study

In this research, the ductile fracture of ultra-fine-grained copper was investigated. Ultra-fine-grained copper was produced using equal channel angular pressing process. During this process, the average grain size of the copper specimens decreases. Experiments have shown that stress state has significant effect on fracture behavior and should be included in the constitutive models. Therefore, the ductile failure was analyzed here by focusing on its relationship with the effect of hydrostatic pressure and Lode angle parameter. Tensile tests were performed on smooth and notched round bar specimens as well as doubly grooved samples. Moreover, the fracture surfaces were investigated by a scanning electron microscope. The experimental results reveal that the stress triaxiality and Lode angle parameter have a remarkable effect on the ductile fracture of the ECAPed specimens. However, the effect of stress triaxiality on ductility reduction is more significant than the effect of the Lode angle parameter. Also, the experimental results show the transition from the tensile ductile fracture to shear fracture in the ECAPed specimens.