Microstructures and properties of Cu/Ag(Invar) composites fabricated by powder metallurgy

The Ag (Invar) composite powder prepared by ball milling was used to fabricate the Cu/Ag (Invar) composites. Microstructures and properties of the composites were studied after sintering and thermo-mechanical treatment. The results indicate that during ball milling, micro-forging weld and work-hardening fracture result in that the average particle size of the Ag (Invar) powder increases rapidly at first, and then decreases sharply, finally tends to be constant. Compared with the Cu/Invar ones, the sinterability of the composites is greatly improved, resulting in that the pores in them are smaller in amount and size. After the thermo-mechanical treatment, the Cu/Ag (Invar) composites are nearly fully dense with the optimum phase composition and element distribution. More importantly, Cu and the Invar alloy in the composites distribute continuously in a three-dimensional (3D) network structure. Cu/Invar interface diffusion is effectively inhibited by the Ag barrier layer, leading to a great improvement of the mechanical and thermal properties of the Cu/Ag (Invar) composites.