Strengthening CoCrNi medium-entropy alloy by tuning lattice defects

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 (similar to 30 mu m) and ultrafine grains (similar to 1 mu m), together with the high density of dislocation cells, small stacking faults, ultrafine nanotwins (similar to 9 nm in thickness) and Lomer-Cottrell locks. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.