Nathan Curtis

Most of the face-centered cubic (FCC) multi-principal element alloys (MPEAs) developed thus far contain cobalt. For many applications, it is either required or beneficial to avoid cobalt, since cobalt has long-term activation issue (for nuclear applications), is expensive, and is considered a critical material. In addition, FCC structured solid-solution MPEAs tend to have relatively low strength. A FCC solid-solution Fe30Ni30Mn30Cr10 (at %) MPEA was fabricated via arc melting, followed by homogenization at 1100 °C for 12 h. The alloy was hot rolled at 1100 °C with a total reduction of up to 97 %. The microstructure was characterized and mechanical properties were investigated at various stages. Tensile testing showed that yield strength (YS) increased by 285–595 MPa and ultimate tensile strength (UTS) increased by 520–710 MPa. This increase in YS and UTS occurred with a total elongation (ductility) of 40 %. Meanwhile, hot rolling at high reductions led to evident decreases in size and area fraction of Mn-rich inclusions. Overall, after hot rolling, this FCC solid-solution MPEA is both strong and ductile.

While ion-irradiation studies are a critical first step in studying compositionally complex alloys (CCAs) for nuclear applications, they do not capture all the microstructural changes occurring under the low irradiation dose rates and different particles’ scattering patterns experienced in a nuclear reactor setting. To explore these phenomena in reactor-relevant conditions for the first time in CCA, the single-phase solid-solution Cr10Fe30Mn30Ni30 was neutron irradiated up to 6.61 displacements per atom at 395 and 579 °C. Irradiation-enhanced local chemical ordering (LCO) well beyond the range of short range ordering was observed, and is predicted to be the precursor to the precipitation of a coherent Ni-Mn L10 phase and a Cr-rich α’ phase, though TEM analysis did not indicate the presence of either in any irradiation condition. The line density of faulted dislocation loops decreased from 6.47 to 1.69 ∙ 1015 m−2 from 3.43 to 6.61 dpa at 579 °C despite no appreciable faulted loop content in the unirradiated material. LCO is expected to increase the complexity of the energy landscape within this alloy, restricting interstitial point defect mobility and creating local regions of greater stacking fault energy. These contribute to the negative correlation between irradiation dose and faulted dislocation loop density in this study, as well as the lack of void swelling observed.

Developing advanced materials for plasma-facing components (PFCs) in fusion reactors is a crucial aspect for achieving sustained energy production. Tungsten (W) − based refractory high-entropy alloys (RHEAs) have emerged as promising candidates due to their superior radiation tolerance and high-temperature strength. This review paper will focus on recent advancements in W-based RHEA research, with particular emphasis on: predictive modelling with machine learning (ML) to expedite the identification of optimal RHEA compositions; additive manufacturing (AM) techniques, highlighting their advantages for rapid prototyping and high-throughput multi-compositional sample production; mechanical properties relevant to PFC applications, including hardness, high-temperature strength, and ductility; and the radiation tolerance of W-based RHEAs under irradiated conditions. Finally, the key challenges and opportunities for future research, particularly the holistic analysis of candidate compositions as well as the role of radiation activation and oxidation are identified. This review aims to provide a comprehensive overview of W-based RHEAs for fusion applications and their potential to guide the development and validation of advanced refractory high entropy alloys.