Optimizing the coupled effects of Hall-Petch and precipitation strengthening in a Al 0.3 CoCrFeNi high entropy alloy

A successful demonstration of applying integrated strengthening using Hall-Petch strengthening (grains size effect) and precipitation strengthening is shown in the fcc based high entropy alloy (HEA) Al0.3CoCrFeNi, leading to quantitative determinations of the Hall-Petch coefficients for both hardness and tensile yield strength, aswell as the enhancements in the yield strength fromtwo distinct types of ordered precipitates, L12 and B2. An excellent combination of yield strength (~490MPa), ultimate tensile strength (~850MPa), and ductility (~45% elongation) was achieved by optimizing and coupling both strengtheningmechanisms, resulting from a refined grain size as well as both L12 and B2 ordered precipitates. This opens up new avenues for the future development of HEAs, with the appropriate balance of properties required for engineering applications.