Twenty years of the CoCrFeNiMn high-entropy alloy: achieving exceptional mechanical properties through microstructure engineering

The CoCrFeNiMn multicomponent is one of the most widely and best studied of all high-entropy alloys (HEAs) since its exceptional properties suggest potential uses as a structural material in many industrial applications. In practice, a good balance between strength and ductility is one of the most important challenges in developing alloys in modern materials science and engineering. There have been many attempts to overcome the strength-ductility trade-off in the CoCrFeNiMn alloy due to its relatively low strength. These attempts include adding a minor sixth element, such as oxide or carbide particles, and also developing thermomechanical processing for grain refinement or precipitation to produce a tailored microstructure with optimum mechanical properties. This review describes the deformation mechanisms and the microstructural evolutions in this alloy during plastic deformation under different conditions of temperature, strain and strain rate where these are important for the processing and manufacturing of the alloy. In addition, this study provides a perspective on the behavior of the alloy under high temperature exposure and also under cyclic loading which is generally the most important factor in industrial applications. This understanding demonstrates that there is a very large potential for the future enhancement and optimization of this and other comparable HEAs.