The effect of yttrium oxide on the sintering behavior and hardness of tungsten

In this study, the relative density and hardness of Y₂O₃ dispersed tungsten alloy were investigated as functions of the Y₂O₃ content and sintering temperature. The sintering temperature and the amount of the second phase were varied from 1800 to 2500°C and 0 to 2.0 weight pct, respectively. The relative density of the alloys is higher than that of pure tungsten in the range from 2000 to 2500°C, whereas the density is lower at 1800°C. As the Y₂O₃ content increases, the sintered density increases at a given temperature. The transition temperature (T_tr), where the relative density of the alloys exceeds that of pure tungsten, is reduced with increased Y₂O₃ particle content. In order to examine the effect of the second phase on the mechanical property, the hardness of pure tungsten and the alloys are measured. The hardness is mainly dependent upon the relative density of the alloys, rather than the amount of the second phase and tungsten grain size. The relationship between hardness and density is discussed according to the plasticity theory of porous materials.