Thermal conductivity and deuterium/helium plasma irradiation effect of WTaCrVTi high entropy alloy

A refractory WTaCrVTi high-entropy alloy (HEA) film was prepared by magnetron sputtering, and a pure tungsten (W) film was also prepared in the same way used as a comparison sample. The electrical resistivity of the films in the temperature range of 4 K - 300 K was measured by the standard four-probe method and the results showed that the resistivity of the HEA film is about 10 times higher than that of the W film. Furthermore, the thermal conductivity of the film sample is calculated by Wiedemann-Franz law. The results show that the thermal conductivity of the HEA film at 300 K is about 10 times lower than that of the W film. Deuterium and helium retention and desorption behavior induced by deuterium and helium plasma exposure of the two films were investigated. The total deuterium retention measured by thermal desorption spectra (TDS) in the HEA film was approximately 16 times larger than that in the W film, which was attributed to the existence of more grain boundary defects and vacancy-type defects in HEA film, leading to more deuterium trapped. The characteristics of helium bubbles in the two films were compared. The results showed that the helium bubbles in the HEA film had a shallower depth distribution and smaller size than those in the W film, which indicated that the bubbles growth evolution was suppressed in the HEA film compared to the W film. It is suggested that helium atoms in the HEA film experience larger lattice potential energy fluctuations due to the abundant hopping processes during diffusion and aggregation.