Microstructural refinement and mechanical property improvement of copper and copper-Al_2O_3 specimens processed by equal channel angular extrusion (ECAE)

摘要

Pure copper and copper alloys containing different volume fractions of nano size Al_2O_3 dispersoids were processec by ECAE at 25-250 deg C, annealed at 25-500 deg C, and microstructural refinement and mechanical property improvement were studied. In samples processed by ECAE to strains of 5, hardness values increased by 100percent in copper specimens and 40-50percent in Cu-Al_2O_3 specimens. A drastic increase in hardness was observed after a strain of 1, and hardness values leveled off beyond a strain of 2. Samples were annealed at 25-500 deg C, to determine the extend of recovery of hardness values. In ECAE processed copper samples, significant reduction in hardness occurred between 100-200 deg C, and higher temperature annealing resulted in hardness values close to the values before ECAE processing. However, in Cu-Al_2O_3 specimens, the increased hardness was maintained in samples annealed at as high as 500 deg C. Strength and ductility values determined from 3 point bend tests showed strength values of 150-200 MPa for copper and 650-800 MPa for Cu-Al_2O_3 samples with excellent ductility in copper as well as Cu-Al_2O_3 samples. The observed results were analyzed in terms of the magnitudes of strengthening contributions from dislocation substructure, fine grains, and incoherent dispersoids.