The effect of Al addition on solid solution strengthening in CoCrFeMnNi: Experiment and modelling

The effect of aluminum addition to the Cantor alloy in the composition range of 0.25–5 atomic percent towards solid solution strengthening of supposedly single-phase HEA was investigated using experiments and first principle simulation-guided constitutive modeling. The continuous increase in yield and tensile strength without significant change in ductility is observed for the alloys with increasing aluminum content. The constitutive modeling of the strengthening has been performed using traditional as well as recently developed models for solid solution strengthening. It indicated a significant contribution (50% increases from Cantor alloy to Cantor alloy containing 5 atom % Al) of solid solution strengthening due to the addition of Al having a relatively larger size (̴12 %) than the size of elements in the Cantor alloy, causing severe local lattice distortion. The experimental yield strength could be best explained based on the large apparent distortion volume of the Al atom acting as a stronger barrier to dislocation motion based on the Varvenne model by incorporating the lattice distortion. First-principles simulations indicate that local and global lattice distortion contributes to an increase in the strength by strong pinning of dislocations by aluminum atom leading to high strength.