Freeze-casted tungsten skeleton reinforced copper matrix composites

Copper-tungsten (Cu-W) composites with a copper content larger than 50 vol% are expected to have a good combination of electrical conductivity and mechanical properties. However, it is difficult to synthesize these types of composites using the conventional manufacturing routes. In this paper, W skeletons with a high porosity up to 80 ± 0.8% and well-aligned microstructures were prepared by directional solidification of aqueous slurries of W followed by ice sublimation and heat treatment. Tungsten reinforced copper matrix composites (e.g., Cu-15 vol% W composites) were fabricated by infiltration of Cu into the W skeleton structures, and their microstructure, electrical conductivity and mechanical properties were studied. The synthesized Cu-15 vol% W composites exhibited alternately patterned Cu and W microstructures and showed a good combination of electrical conductivity of 78 ± 2% IACS and hardness of 136 ± 6HV. The strengthening mechanisms of these Cu-15 vol% W composites were identified as the formation of tungsten network structures which support and strengthen the copper matrix. Residual pores in the W lamellae and weak interfaces of copper-tungsten caused the initiation and propagation of cracks, and the fracture mode of Cu-15 vol% W composite was polymerization induced ductile fracture.