Development of ultra-fine grained W–TiC and their mechanical properties for fusion applications

Abstract Effects of neutron irradiation on microstructural evolution and radiation hardening were examined for fine-grained W–0.3 wt%TiC (grain size of 0.9 μm) and commercially available pure W (20 μm). Both materials were neutron irradiated at 563 K to 9 × 1023 n/m2 (E > 1 MeV) in the Japan Materials Testing Reactor (JMTR). Post-irradiation examinations showed that the microstructural changes and the degree of hardening due to irradiation were significantly reduced for fine-grained W–0.3TiC compared with pure W, demonstrating the significance of grain refinement to improve radiation resistance. In order to develop ultra-fine grained W–TiC compacts with nearly full densification, the fabrication process was modified, so that W–(0.3–0.7)%TiC with 0.06–0.2 μm grain size and 99% of relative density was fabricated. The achievable grain refinement depended on TiC content and milling atmosphere. The three-point bending fracture strength at room temperature for ultra-fine grained W–TiC compacts of powder milled in H2 reached approximately 1.6–2 GPa for composition near 0.5%TiC.