Effects of Al and Mn on microstructure, magnetic and mechanical properties of Fe40Co40Ni10M10 (M=Al, Mn) medium entropy alloys

Abstract The influences of Al and Mn on microstructure, magnetic and mechanical properties of Fe40Co40Ni10M10 (M = Al and Mn) medium entropy alloys (MEAs) have been systematically investigated. It is found that the Fe40Co40Ni10Al10 has body-centered cubic (BCC) structure and Fe40Co40Ni10Mn10 has a mixture of face-centered cubic (FCC) and BCC structures in as-cast state, while the former one changes to FCC + BCC dual-phase structure after heat treatment at 1073 K for 1 h. Fe40Co40Ni10Al10 displays higher saturated magnetization (Bs) as compared to Fe40Co40Ni10Mn10 in as-cast state, while heat treatment significantly enhances Bs of Fe40Co40Ni10Mn10. Besides, it is intriguing that Fe40Co40Ni10Mn10 shows higher yield strength and plasticity compared to Fe40Co40Ni10Al10, while heat treatment could enhance comprehensive mechanical properties of this series of MEAs. In addition, the Bs of heat-treated Fe40Co40Ni10Mn10 is 187.9 emu/g, which is among the highest in the reported ferromagnetic HEAs/MEAs. The correlation among the composition, phase evolution, magnetic properties, and mechanical properties in these MEAs is discussed in detail. This work provides a novel route for developing high-performance ferromagnetic HEAs/MEAs.