Microstructure tailoring by manipulating chemical composition in novel CoNiMnCrAl high-entropy alloys

One of the most important dilemmas in materials science is to overcome the strength-ductility trade-off. There is an increasing trend toward designing alloys with strong precipitates in order to tackle this issue. The brittle sigma phase, a prevalent precipitate in high-entropy alloys, is responsible for the deterioration of the mechanical properties. In this research, a novel Fe-free high-entropy alloy based on Co-Cr-Ni-Mn-Al is introduced with no potential for sigma formation to develop an alloy with a good combination of strength and ductility. Thermodynamic predictions and elemental functions suggested three FCC single-phase high-entropy alloys including Co25Ni30Mn30Cr10Al5, Co30Ni25Mn30Cr10Al5 and Co30Ni30Mn25Cr10Al5 (all in at%) alloys with no sigma phase formation. It was shown that the addition of a minor amount of Al made precipitation hardenable alloys to improve strength due to encouraging the formation of a controlled amount of desirable NiAl-B2 precipitates in the microstructure. The alloys were fabricated and conducted to severe cold rolling followed by short-term annealing at 1000 °C to microstructure engineering and improve strength with no scarifying ductility. The Co30Ni25Mn30Cr10Al5 alloy with low stacking fault energy, fine grain size, high area fraction of twins, and formation of fine precipitates in the microstructure represented a very good combination of strength and ductility. / 1 / 1 / N / scie / scopus