Effects of raw materials on microstructure and mechanical properties of second phase particles reinforced WRe composites

Abstract

Combined strengthening of micron and nanoscale second phase particles is of great significance for improving the comprehensive properties of tungsten (W) based refractory alloys. In this work, with the addition of raw HfC, HfH₂ and carbon powders, three types of W-3 wt%Re-0.3 wt%HfC (WRH) composites were fabricated by powder metallurgy and rotary swaging. The microstructure and mechanical properties of three WRH samples were investigated comparatively. Results show that three WRH samples are constituted by W matrix, HfO₂ and HfC second phase particles. When HfH₂ powder is served as the raw material, the obtained two kinds of composites show the microstructure configuration with a micro-nano combined second phase particles. That is, some larger HfO₂ particles are located at the matrix grain boundaries and fine nanoscale HfC particles are inside W matrix grains. Based on it, both composites exhibit the better overall performance. When the carbon powder ratio reaches 0.03 wt%, WRH composite shows the smallest average matrix grain size and a smaller size of second phase particles inside the matrix grains, and thereby gaining the better ultimate tensile strength and hardness. As carbon powder ratio rises to 0.07 wt%, WRH sample presents an excellent elongation. Besides, the formation mechanisms of HfO₂ and HfC particles, as well as the correlation between microstructure and mechanical properties, were discussed particularly.