Evolution of Phase, Microstructure and ZrC Lattice Parameter in Solidsolution-treated W-ZrC Composite

Zirconium carbide (ZrC) reinforced tungsten (W) composite was hot-pressed at 2200 degrees C for 1h in vacuum, which was subsequently heat treated in the temperature range of 2200 to 2500 degrees C for 1.5 or 2h. The relative ratios of ZrC phase were 21.0, 23.3 and 25.9 mol.% for the mixture of starting powders, composites sintered for 1 h and solid-solution treated at 2500 degrees C for 1.5h, respectively. The solid solubility of W in ZrC increased with the increment in heat-treating temperature and time to a maximum value of 18.9 mol.% at 2500 degrees C for 1.5 h. The lattice parameter of cubic ZrC phase diminished from 0.4682 nm in the starting powder to 0.4642 nm in the solid-solution composite treated at 2500 degrees C for 1.5h. This work demonstrated that the relationship between the solid solubility of W in ZrC and the lattice parameter of ZrC is linear, with a slope of-1.93 X 10(-4)nm/at.%. Overall, more W atoms diffused into ZrC lattice after heat treatment, meanwhile, the previous precipitated nano-sized W dissolved in the supersaturated (Zr,W)C solid-solution, as detected by SEM and TEM.