Refractory High-Entropy Alloys for Fusion Reactor Plasma-Facing Components Under Extreme Heat Flux

High-Entropy Alloys (HEAs) have emerged as a transformative class of materials for fusion reactor plasma-facing components (PFCs), offering exceptional resistance to extreme heat fluxes, irradiation damage, helium blistering, and tritium retention. Fusion reactors. such as ITER, DEMO, ARC, and SPARC impose unparalleled thermomechanical and plasma-material interaction (PMI) challenges, including steady- state heat loads of 10–30 MW/m², transient disruption pulses reaching 100–200 MJ/m²·s, helium ion implantation leading to bubble formation and surface exfoliation, and neutron fluxes surpassing 10¹⁵ n/cm²·s. Conventional PFC materials including tungsten,tungsten-rhenium alloys, and advanced ceramics exhibit severe limitations: cracking under thermal shocks, high sputtering rates, radiation-induced embrittlement, and unsafe levels of tritium retention. HEAs, leveraging their multi-principal-element chemistry, severe lattice distortion, sluggish diffusion, and superior radiation resistance, offer enhanced microstructural stability, reduced helium bubble formation, lower sputtering yields, and dramatically reduced hydrogen isotope retention. This paper presents a comprehensive investigation into the suitability of HEAs for next-generation fusion reactor PFCs, exploring their thermodynamics, microstructural evolution, plasma erosion behaviour, irradiation tolerance, thermal shock performance, and multi-physics PMI response. The analysis demonstrates that HEAs represent one of the most promising material platforms for enabling reliable, long-duration, high-power fusion reactor operation.