Microstructure and Mechanical Properties of Face‐Centered‐Cubic‐Based Cr‐Free Equiatomic High‐Entropy Alloys

High‐entropy alloys (HEAs) with face‐centered‐cubic (FCC) structures, e.g., the typical CrMnFeCoNi HEA, have a strong tendency to precipitate brittle sigma phases, as Cr is a strong sigma stabilizer. To develop HEAs with alleviated concerns of sigma phases, Cu for Cr in the Cr‐Mn‐Fe‐Co‐Ni HEA system is substituted to form a Mn‐Fe‐Co‐Ni‐Cu system. The quinary alloy and its quaternary subsets are investigated all in as‐cast state. Microstructure evolution, phase constituent, and tensile properties at room temperature are studied. The HEAs have multi‐phase FCC structures with slightly different lattice constants and spherical Cu‐rich particles are observed in most systems. All alloys exhibit dendrite‐like morphology with Cu segregation in interdendritic regions due to the solute partitioning. The investigated HEAs show good strengths, large elongations, and work hardening capability. The strengths are attributed to combined mechanisms, especially the precipitation strengthening by Cu‐rich particles. The findings provide some model HEA systems for further usefully guiding design in the widely compositional space of Cr‐free HEAs. Microstructures and tensile properties of the Cr‐free MnFeCoNiCu high‐entropy alloy and its quaternary equatomic subsets are present. The alloys consist of multi‐phase face‐centered‐cubic structures with typical dendrites and spherical Cu‐rich particles in Cu‐segregated regions. The alloys show good strengths, large elongations and work hardening capability, which may provide model systems for further guiding design of Cr‐free high‐entropy alloys.