Abstract:The microstructure evolution, dislocation density and mechanical properties of pure copper via equal channel angular pressing were studied to investigate the effects of stack fault energy on the microstructure evolution. The results show that the grain size of annealed pure copper is refined into 5-10 μm, the small grain boundary turns into large ones, subsequently. The dislocation density is 0.16×10¹⁴ m^-2 after 1 pass and reaches the maximum of 0.41×10¹⁴ m^-2 after 6 passes, which increases remarkably with increasing the passes. While the recombination and annihilation of dislocations give rise to subsequent density decrease. The tensile strength of annealed copper is 220 MPa with elongation of 53.5%, while the tensile strength reaches 444 MPa and elongation reduces to 22.1% after 8 passes, which reveals that ECPA leads to the improvement of tensile strength and reduction of plasticity. The increased shallow dimple amounts and more uniform distribution of pure copper reveal its ductile fracture mechanism. The results of the microstructure evolution and mechanical property analysis show that, pure copper, as the middle stack fault energy metal material, possesses the characteristic of metal materials with high or low stack fault energy.

Key words: pure copper; ECAP; dislocation density; mechanical property; stacking fault energy