Fabrication of W–20 wt % Cu composite nanopowder and sintered alloy with high thermal conductivity

Abstract

The reduced W–20% Cu powder with W particle sizes of about 30–100 nm and uniform distribution of components was successfully synthesized by mechano-thermochemical process. This process consists of three steps: the producing of oxide powder, the wet ball milling of oxide powder and the final reduction. W/Cu composite oxide clusters with a spherical shell structure were prepared by spray drying of aqueous solution of Cu and W salts with subsequent oxidation at 750 °C for 2 h. These oxide clusters were fragmented to fine oxide powders by wet milling and reduced at 600–800 °C in hydrogen. The sintering behavior of composite powder and thermal conductivity of sintered alloys were also investigated. This composite powder showed higher sinterability comparatively with conventional blended powders. The thermal conductivity of W–20% Cu alloys prepared by this work is 239±5.0 W/mK, which is equal to the theoretical value. Superior properties of the present powder are due to the homogeneous mixing state of nanosized W and Cu particles in powder, homogeneous redistribution of W solid particles in liquid Cu and high purity of powder. This alloy did not contain such impurities as Fe and Co that can be easily introduced in powder in conventional processing.