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

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, HfH 2 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, HfO 2 and HfC second phase particles. When HfH 2 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 HfO 2 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 HfO 2 and HfC particles, as well as the correlation between microstructure and mechanical properties, were discussed particularly. • HfO 2 and HfC are the important second phase reinforcement particles. • HfO 2 and nanoscale HfC particles are located respectively at GBs and interior of W grains. • Formation mechanism of HfO 2 and HfC second phase particles is proposed.