Effect of Cumulative Multipass Continuous Extrusion on Microstructure and Mechanical Properties of Pure Copper

The cumulative multipass continuous extrusion process was used to conduct multipass continuous extrusion for pure copper by means of continuous feeding. The microstructure evolution and mechanical properties of pure copper rod were observed and tested by optical microscope, scanning electron microscope（SEM） and electronic universal material testing machine, and the effect of extrusion pass on the microstructure and mechanical properties of pure copper rod was discussed.The results show that after one continuous extrusion, the tensile strength of pure copper rod material increases from 178.21 MPa to 239.61 MPa, and the elongation increases from 41.72% to 52.43%. As the number of extrusion passes increases, the tensile strength and elongation of pure copper rod material first increase and then decrease. After two cumulative extrusion passes, the tensile strength of pure copper rod material reaches its maximum value, which is 248.03 MPa and 56.51%,respectively. As the number of extrusion passes increases, the average grain size of pure copper rod material first decreases and then gradually increases. After two continuous extrusion passes, the average grain size is smallest, the dimples of the tensile fracture is deepest and evenly distributed, and the overall mechanical properties are best.