Design principles of low-activation high entropy alloys

The present study combines density functional theory (DFT) based calculations and experimental techniques to investigate the formation of equiatomic quaternary “low-activation" high entropy alloys (HEAs) for nuclear fission/fusion applications. DFT based techniques are adopted to screen the formation of possible single-phase ternary and quaternary alloys in chemical space consisting of the low-activation elements (Ti, V, Cr, Mn, Fe, Ta and W). The results indicate that TaTiVW and CrFeMnV can be formed in a single body centred cubic phase (BCC). Based on the DFT based screening, HEAs are fabricated by a vacuum arc melting process. Further characterisation by X-ray diffraction, energy dispersive X-Ray analysis, X-ray fluorescence and scanning electron microscopy confirms the formation of TaTiVW in a BCC single phase. Microstructures of CrTiVW and CrTaVW in as-cast conditions, consist of two BCC phases with very similar lattice parameters. CrTaTiW and CrTaTiV showed evidence of C15 Laves formation comprising of TaCr₂ and TiV₂, respectively.