Effect of post-annealing on microstructure and mechanical properties of copper tube produced by severe plastic deformation
Abstract:
The aim of this study was to investigate the effect of post-annealing on microstructure and mechanical properties of copper tube produced by severe plastic deformation (SPD). For this purpose, copper tube by tube cyclic extrusion–compression (TCEC) at room temperature up to 2 cyclic undergone SPD process. Then, for estimated the recrystallization temperature of 2- cyclic sample, the annealing was carried out at temperatures from 100 ° C to 300° C with intervals of 50 ° C. The thermal stability diagram (temperature vs hardness) was plotted and recrystallization temperature was determined about 200 ° C for 2 cycles-TCEC samples. According to recrystallization temperature, 1 and 2 cycles-TCEC samples were annealed at 150° C for 20 min (the temperature that is lower than the recrystallization temperature) and then microstructure and mechanical properties were investigated. The obtained results showed that, significant grain refinement resulted to a mean grain size of 4.5 µm was achieved even after a single cyclic TCEC. The yield strength and ultimate tensile strength after the 1 cycles-TCEC was increased approximately 108% and 13% of the initial sample respectively. By Increasing the level of accumulated strain to 4.66 in cyclic 2, a large amount of finer boundary spacing is observable. Yield strength and ultimate tensile strength increased by 272 MPa and 283 MPa respectively after 2-cyclic TCEC. On the other hand, the better mechanical properties were observed in the material produced by subsequently annealed. The results indicate that, the strength of samples with post annealing at 150° C for 20 min has been improved.