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

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 mu m) and commercially available pure W (20 mu m). Both materials were neutron irradiated at 563 K to 9 x 10(23) n/m(2) (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 to fine-grained W-0.3TiCcompared 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 mu m 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 H, reached approximately 1.6-2 GPa for composition near 0.5%TiC. (C) 2007 Elsevier B.V. All rights reserved.