# Thermal Stability and Irradiation Resistance of (CrFeTiTa)70W30 and VFeTiTaW High Entropy Alloys

## TL;DR

This paper studies two high-entropy alloys for use in nuclear fusion reactors, focusing on their ability to withstand high heat and radiation.

## Contribution

The study evaluates the thermal and irradiation resistance of (CrFeTiTa)70W30 and VFeTiTaW alloys for nuclear fusion applications.

## Key findings

- Both alloys showed phase growth after high-temperature annealing, with VFeTiTaW showing more growth.
- Irradiation tests showed no severe surface changes, indicating high irradiation resistance.
- VFeTiTaW retained less deuterium compared to (CrFeTiTa)70W30 after irradiation.

## Abstract

Nuclear fusion is a promising energy source. The International Thermonuclear Experimental Reactor aims to study the feasibility of tokamak-type reactors and test technologies and materials for commercial use. One major challenge is developing materials for the reactor’s divertor, which supports high thermal flux. Tungsten was chosen as the plasma-facing material, while a CuCrZr alloy will be used in the cooling pipes. However, the gradient between the working temperatures of these materials requires the use of a thermal barrier interlayer between them. To this end, refractory high-entropy (CrFeTiTa)70W30 and VFeTiTaW alloys were prepared by mechanical alloying and sintering, and their thermal and irradiation resistance was evaluated. Both alloys showed phase growth after annealing at 1100 °C for 8 days, being more pronounced for higher temperatures (1300 °C and 1500 °C). The VFeTiTaW alloy presented greater phase growth, suggesting lower microstructural stability, however, no new phases were formed. Both (as-sintered) alloys were irradiated with Ar+ (150 keV) with a fluence of 2.4 × 1020 at/m2, as well as He+ (10 keV) and D+ (5 keV) both with a fluence of 5 × 1021 at/m2. The morphology of the surface of both samples was analyzed before and after irradiation showing no severe morphologic changes, indicating high irradiation resistance. Additionally, the VFeTiTaW alloy presented a lower deuterium retention (8.58%) when compared to (CrFeTiTa)70W30 alloy (14.41%).