Optimizing mechanical and magnetic properties of AlCoCrFeNi high-entropy alloy via FCC to BCC phase transformation

Abstract FCC, BCC and B2 phases, the most common phases in high-entropy alloys (HEAs), are widely investigated to tailor their mechanical and magnetic performances. The detailed investigation of FCC to BCC/B2 phase transformation of AlCoCrFeNi HEA in this paper reveals its evolution and structure-properties relations in terms of both temperature and holding duration. With increasing heat treatment temperature and duration, such transition will progress simultaneously at both the dendric core (DC) region and inter-dendric (ID) region and the volume of phase transformation from FCC to BCC phases is greater than FCC to B2 phases, resulting in increased yield strength and saturation magnetization. The obvious phase transition of the AlCoCrFeNi HEA at 1200 °C can enhance its yield strength and saturation magnetization as a sacrifice of its fracture strain. However, an excellent combination of mechanical-magnetic properties was achieved when heat-treated at 1100 °C for 50 h by optimizing both the transformation and the size of B2 phases. Our present study could pave ways to design the HEAs or other alloys with an optimum combination of mechanical and magnetic properties for application-oriented viewpoints.