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, σ phase and finely dispersed precipitates. This has been achieved by casting CoCrFeMnNiV 0.5, CoCrFeMnNiMo 0.5 and CoCrFeMnNiV 0.5Mo 0.5 at. % HEAs at a cooling rate of ∼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 μm for CoCrFeMnNi, to ∼89 μm and ∼85 μm for the FCC and σ phases, respectively in the CoCrFeMnNiV 0.5Mo 0.5 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 CoCrFeMnNiV 0.5, 4.78 GPa for CoCrFeMnNiMo 0.5 and 6.85 GPa for CoCrFeMnNiMo 0.5V 0.5 thus making these alloys of potential interest for engineering components subjected to load and wear.