Strengthening CoCrNi medium-entropy alloy by tuning lattice defects

Abstract The CrCoNi medium-entropy alloy is not fully utilized at room temperature circumstance due to its low strength, despite excellent cryogenic mechanical properties. Here we report that, a superior room temperature strength (1.6 GPa and 407.6 Hv) has been obtained in the single phase CoCrNi medium-entropy alloy, by carefully tuning the formation of multiple lattice defects. Electron microscopy characterizations show that such high-strength CoCrNi alloy contains favorable heterostructures of coarsening grains (~30 μm) and ultrafine grains (~1 μm), together with the high density of dislocation cells, small stacking faults, ultrafine nanotwins (~9 nm in thickness) and Lomer–Cottrell locks.