Synergistic enhancement of strength-ductility in ODS copper alloy by exploring heterogeneous structure

Abstract

This work presents a novel one-step extrusion method for preparing Al₂O₃ nanoparticles dispersion strengthened (ODS) copper with heterogeneous structure, overcoming the strength-ductility trade-off dilemma. Ultrafine Cu-0.75 wt% Al alloy powder produced by gas-water combined atomization was processed into ODS copper powder through oxidation in air at 350 °C, further diffusion of oxygen in copper matrix in nitrogen at 450 °C, and then reduction in hydrogen at 650 °C. High-energy ball milled ODS copper powder was loosely sintered and subsequently extruded into ODS copper rods. The results show that the heterogeneous structure consisted of ultrafine grains in ODS copper and coarse grains in pure copper was formed after annealing of hot extruded ODS copper rods. The ultrafine grains were attributed to the strong pinning effect of Al₂O₃ nanoparticles on grain boundary migration, while coarse grains were due to recrystallization growth of grains derived from the sintering and hot extrusion of unexpected pure copper particles on the surface of the ODS copper powder. Owing to comprehensive strengthening mechanisms of dispersion strengthening, grains refinement, and hetero-deformation induced strengthening, compared to the as-extruded homogeneous structure, the annealed ODS copper with heterogeneous structure amazingly exhibited a 64 % increase in elongation while maintaining an excellent tensile strength of 565 MPa, significantly higher than previous work reported. These findings can provide insights into the synergistic enhancement of strength-ductility in novel copper alloys.