Research and development on vanadium alloys for fusion applications

The current status of research and development on unirradiated and irradiated V-Cr-Ti alloys intended for fusion reactor structural applications is reviewed, with particular emphasis on the flow and fracture behavior of neutron-irradiated vanadium alloys. Recent progress on fabrication, joining, oxidation behavior, and the development of insulator coatings is also summarized. Pronounced flow localization and loss of strain hardening capacity with uniform elongations <1% generally occurs in vanadium alloys for irradiation temperatures below similar to 400 degrees C (0.31 T-M). These changes in tensile properties for T-irr < 400 degrees C are generally accompanied by large increases in the ductile-to-brittle transition temperature measured under both dynamic and quasi-static loading conditions. The relationships between radiation hardening, flow localization, strain rate, and fracture properties are examined. The irradiated mechanical properties at temperatures between 430 degrees C and 650 degrees C are acceptable for most structural applications. Further work is needed to determine how far the allowable lower and upper operating temperature limits can be expanded beyond the 430-650 degrees C range. (C) 1998 Elsevier Science B.V. All rights reserved.