Microstructure evolution and mechanical property of W-Ni3Al alloy by adding minor Co element

Abstract

In this study, W-Ni3Al alloys with fine grain size and outstanding integrated mechanical properties were fabricated based on mechanical alloying and spark plasma sintering (SPS), modified by adding a small amount of cobalt powder. It was found that the alloy was strengthened by the diffusion of Co and W elements into the Ni3Al lattice to form (Ni,Co)3(Al,W) solid solution during the sintering, where Al2O3 particles in-situ formed at the interface between binder phase and tungsten grains, and therefore became obstacles to impeding the dislocation movement. Such obstacles would lead to restraints of dissolution-reprecipitation of tungsten grains, resulting in refined tungsten grains and strengthening effect in the sintered alloys. The synergistic effect of these two kinds of strengthening significantly improved the mechanical properties of W-Ni3Al alloy. As a result, the W-9Ni3Al-1Co alloy sintered at a low temperature of 1250 °C had the best room-temperature mechanical properties, and its bending strength, tensile strength and hardness were 1519.48 MPa, 783.24 MPa and 71.1 HRA, respectively.