Cooling rate control combined with refractory Mo and/or V addition to enhance the mechanical properties of CoCrFeMnNi alloy

This work shows that optimum combination of cooling rate control and refractory Mo and/or V element addition to the CoCrFeMnNi (Cantor) HEA enables to develop novel high-strength hierarchical microstructures consisting of FCC, sigma phase and finely dispersed precipitates. This has been achieved by casting CoCrFeMnNiV0.5, CoCrFeMnNiMo0.5 and CoCrFeMnNiV0.5Mo0.5 at. % HEAs at a cooling rate of similar to 1000 K/s. Since this cooling rate is relatively fast, it enables to retain the Mo and/or V alloying elements in solid solution in the FCC phase. The phenomenon of solid solution hardening contributes to a decrease in the maximum indentation depth from 100 mu m for CoCrFeMnNi, to similar to 89 mu m and similar to 85 mu m for the FCC and sigma phases, respectively in the CoCrFeMnNiV0.5Mo0.5 at. % HEA. The novel microstructures additionally improve the wear resistance, particularly regarding the scratch hardness number, from H-s = 2.74 GPa for CoCrFeMnNi, to 4.19 GPa for CoCrFeMnNiV0.5, 4.78 GPa for CoCrFeMnNiMo0.5 and 6.85 GPa for CoCrFeMnNiMo0.5V0.5 thus making these alloys of potential interest for engineering components subjected to load and wear.