Effects of Internal Oxidation Methods on Microstructures and Properties of Al₂O₃ Dispersion-Strengthened Copper Alloys

Abstract

With Cu–Al alloy powder as raw material and Cu₂O powder as oxidant, two internal oxidation methods, namely step-by-step internal oxidation-reduction method (referred to as the step-by-step method) and integrated internal oxidation-reduction method (referred to as the integrated method), were respectively adopted to achieve the oxidation of Al. Then hot extrusion without canning was applied to prepare Al₂O₃ dispersion-strengthened copper alloys. The effects of the two internal oxidation methods on microstructures and properties of the alloys were compared. The results show that both the step-by-step method and the integrated method can achieve the complete oxidation of Al. However, the excessive oxidant can not be reduced thoroughly in the integrated method. The residual oxidant increases oxidation of the sintered body during hot extrusion and the formed copper oxides distribute in the grains as well as at the grain boundaries. While in the step-by-step alloy, the copper oxides mainly distribute at the grain boundaries. The step-by-step method improves electrical conductivity and ductility, but lowers hardness and strength. The integrated alloy has worse ductility and lower electrical conductivity, but strength and hardness are higher. The step-by-step alloy has better comprehensive properties, and its electrical conductivity, hardness, tensile strength, yield strength and elongation is 89% IACS, HRB 69–72, 425 MPa, 394 MPa and 27.2%, respectively.