Studying the effect of forming at the dynamic recrystallization activation threshold temperature on mechanical properties of copper produced by tube cyclic extrusion– compression

In this study, Tube cyclic Extrusion Compression (TCEC) process was performed on copper pipes at ambient and 200°C (dynamic recrystallization activation threshold temperature) and the effect of process temperature on microstructure and mechanical properties were investigated. The results showed that by applying TCEC at ambient temperature, an equiaxed crystalline structure with an average grain size of 370 nm was obtained while by increasing the forming temperature to 200°C, the equiaxed grains with average size of 720 nm resulted. Applying the TCEC process at ambient temperature on a copper tube, increased its yield strength from 116 to 242 MPa and its average hardness from 69.2 to 101.4 Vickers while at the forming temperature of 200°C, the yield and ultimate strength were about 217 and 225 MPa, respectively, and the average hardness value was about 86.8 Vickers. Therefore, performing TCEC process at 200 °C on copper reduced the strength by 10% and increased the elongation to fracture by 21% compared to the cold forming state.