Current status of ultra-fine grained W–TiC development for use in irradiation environments

Abstract

Ultra-fine grained (UFG) W–TiC with a high purity matrix of low dislocation density is expected to exhibit improve resistance to irradiation with neutrons and helium ions and the room temperature mechanical properties. Aiming at such UFG W–TiC with the desired microstructure, powders of W with 0.25–0.8 wt% TiC additions were subjected to mechanical alloying (MA) and hot isostatic pressing (HIP), where purified H2 and Ar were used as the MA atmosphere. Microstructural observations and room- and high-temperature mechanical tests were performed for UFG W–TiC before and after neutron irradiation to a fluence of 2×1024  n m−2 at 873 K. It is shown that the MA atmosphere significantly affects grain refinement, room-temperature strength and high-temperature tensile plasticity of UFG W–TiC. W–0.5TiC with H2 in MA (W–0.5TiC–H2) shows a larger strain rate sensitivity of flow stress, m, of 0.5~0.6 at temperatures from 1673 to 1973 K, which is a feature of superplastic materials. Whereas W–0.5TiC–Ar shows a smaller m value of approximately 0.2. No radiation hardening is recognized in UFG W–0.5TiC–H2 and W–0.5TiC–Ar.