Evaluation of thermal properties of CuCrFeV (Ti, Ta, W, Mo) for nuclear fusion applications

Abstract

This work investigates the influence of composition on the thermal properties of the high entropy alloy family Cu₅Cr₃₅Fe₃₅V₂₀-X₅ (at. %), where X  = Ti, Ta, W or Mo in the framework of acting as a thermal barrier between the W-based plasma-facing elements and the CuCrZr or Cu-based heat sink components of the fusion reactor. The alloys were produced by arc melting and their microstructure and mechanical properties were previously characterized by XRD, SEM, and Vickers hardness measurements. Thermal properties have been measured on as-cast at thermally treated alloys using the laser flash method in the temperature range 25 °C to 600 °C to determine the thermal diffusivity, α, thermal conductivity, λ, and specific heat, C_p. Dilatometry experiments were also carried out to obtain the linear thermal expansion coefficient, CTE, as a function of temperature.

For all materials, the thermal conductivity increases with temperature from 15 W/m·K at RT to 28 W/m·K at 600 °C and does not significantly depend on the thermal treatment for the Mo-HEA and W-HEA, but increases after aging for the Ta-HEA and Ti-HEA. These values are lower than those of W (∼122 W/m·K at 600 °C) and much lower than for CuCrZr-IG (∼354 W/m·K at 400 °C). The thermal expansion coefficients of these HEAs, ∼10 × 10⁻⁶ °C⁻¹ at RT and ∼ 2 × 10⁻⁶ °C⁻¹ at 650 °C are between those of CuCrZr and the W for the entire operative temperature range. These results indicate that the Cu₅Cr₃₅Fe₃₅V₂₀-X₅ (X = Ti, Ta, W, Mo) HEAs have a promising combination of the thermophysical properties, λ, C_p and CTE, to act as thermal barrier in plasma-facing components that require the union of W- and Cu-based materials.