Elucidating the thermal response of W-Ta alloys with Transient Grating Spectroscopy, TEM and atomistic simulation

Abstract

Critical for tungsten alloys’ use as plasma-facing component materials are their thermal response and their evolution under irradiation. Utilising Transient Grating Spectroscopy, TEM, and Molecular Dynamics, this study sought to probe these changes in W, W6Ta, and W11Ta alloys. Irradiation with 12.25 MeV W${}^{6+}$ ions was carried out in the CLASS facility at MIT at a temperature of 500 °C for doses of 0.1, 0.3, and 1.0 dpa. The alloys’ thermal diffusivity was found to degrade less than that of the pure counterpart. Molecular Dynamics simulation revealed that this was due to a reduced defect population below TEM resolution. Despite these alloys showing enhanced resilience to thermal property degradation, it was found that the absolute values of their thermal diffusivity remained below that of pure tungsten. This study highlighted a key interplay between enhancing radiation tolerance with alloying additions and the alloy additions’ initial negative effect on the thermal response and thus in-service behaviour.