Microstructure of and mechanical properties of an as-cast fine-grain dual-phase Fe-based high entropy alloy formed via solid-state phase transformation

In this paper, a novel Fe49.85Cr10.03Mn10.03Co10.03Ni10.03Al10.03 high entropy alloy (HEA) with dual-phase fine-grain structure was designed and fabricated by arc-melting. Its microstructure, as well as mechanical properties at room temperature and cryogenic temperature, have been systematically investigated. It is found that this as-cast Fe-based HEA is composed of face-centered cubic (FCC) and body-centered cubic (BCC) phases, and the stick-like FCC fine grains are derived from solid-state phase transformation of BCC phase during cooling. Moreover, it shows similar tensile strength and good plasticity at room temperature and cryogenic temperature, indicating high and stable mechanical properties at a wide range of temperatures. This work provides a novel route for designing high-performance fine-grain HEAs without mechanical/heat treatment, which is beneficial for further development of HEAs.