Spinodal decomposition induced nanoprecipitates strengthened CoCrNi-base medium entropy alloy

Precipitation-hardening is an essential and promising method to enhance the strength of alloys. However, this strengthening mechanism will destroy the plasticity of the alloy and lead to premature failure. Here, we report a strategy to improve the strength of the alloy by producing highly-coherent nanoprecipitates (HNPs) through spinodal decomposition. The HNPs can be sheared by dislocations to eliminate the stress concentrations and premature failure. We designed and fabricated a bulk CoCrNiAl0·1Mo0.1 medium entropy alloys (MEAs) to consist of face-centered cubic phase and HNPs structure involving high temperature recrystallized and low temperature aging. Compared with the samples without precipitation, HNPs structure contribute to obtain a satisfactory trade off with the yield strength of 900 MPa, the tensile strength of 1215 MPa and 40% tensile ductility.