Fabrication of Cu-ZrO2 composites by in situ oxidation of liquid Cu–Zr alloy

Zirconia nanoparticle–reinforced copper matrix composites were successfully fabricated using an in situ oxidation technique with liquid Cu–Zr alloy. Cu–1 wt% Zr alloy was oxidized at liquidus temperature under an oxygen potential–controlled N2 atmosphere to yield 2.2 vol% ZrO2 particles ranging from 1 to 20 nm. TEM observation showed a semi-coherent relationship between the dispersoids (monoclinic zirconia) and Cu matrix, with uniform distribution in the Cu–ZrO2 composite. The formation of fine ZrO2 particles in the copper matrix composite was related to the selective oxidation of Zr and isothermal solidification of Cu at the liquidus temperature of the Cu–Zr alloy. A possible formation mechanism for the ZrO2 particles based on oxygen diffusion is proposed; in this model, O atom diffusion is hindered by the formation of a Cu shell on the ZrO2 particles, thereby inhibiting ZrO2 particle growth. The microhardness of the Cu–2.2 vol% ZrO2 composite was 91 HV and the maximum value of electrical conductivity was 93% IACS.