Nano-phase formation accompanying phase separation in undercooled CoCrCuFeNi-3 at.% Sn high entropy alloy

Highlights: • Undercooled multi-component CoCrCuFeNi-3 at.% Sn high-entropy alloy was studied. • Accompanying phase separation, the nano-precipitates were detected. • The effect of Sn on the microstructures and properties was clarified. • The microhardness increased markedly with the increase of undercooling. - Abstract: Highly undercooled multi-component CoCrCuFeNi-3 at.% Sn high-entropy alloy was studied by adopting molten glass purification combined with cycle superheating methods. Based on the critical undercooling ΔT^⁎, the characteristic of liquid-phase separation was researched at different undercoolings. Accompanying phase separation, two phases (CoCrFeNi-rich and CuNi-rich) and three kinds of nano-precipitates (CrCo-rich, CrSn-rich and Sn-rich nano-precipitates) were detected. The microhardness of undercooled CoCrCuFeNi-3 at.% Sn high-entropy alloys increased markedly with the increase of undercooling. The effect of Sn on the microstructure evolution and properties in the process of phase separation was clarified with the aid of nano-precipitates.