Sc diffusion in HCP high entropy alloys

Sc diffusion in hexagonal close packed Al15Hf25Sc10Ti25Zr25 and Al5Hf25Sc20Ti25Zr25 high-entropy alloys is measured using the CERN facility for implantation of the 46Sc isotope. The Sc diffusivity is found to be slower than that of previously measured Ti in both alloys. Ab initio-informed calculations are used to quantify the interplay of chemical complexity and local atomic strains. The mean-square atomic displacements are shown to contribute to the observed "anti-sluggish" diffusion behavior in these high-entropy alloys.