Tailoring mechanical and magnetic properties of AlCoCrFeNi high-entropy alloy via phase transformation

Phase constitutions, either changed by alloying or by phase transformation, are the key factors to determine the magnetic and mechanical performances of high-entropy alloys (HEAs). Using the AlCoCrFeNi HEA as a candidate alloy, this paper demonstrates the effect of phase transformation on both the mechanical and magnetic properties in the multi-phase system. With increasing heat treatment temperature, the sigma (σ) and face-centered-cubic (FCC) phases disappeared at 1000 °C and 1200 °C, respectively. Such volume fraction changes of σ, FCC and body-centered-cubic (BCC) phases have divergent effects on mechanical and magnetic properties. The excellent strength-ductility combination will be achieved as the disappearance of σ phase and formation of FCC phase. As for the magnetic properties, the volume fraction of BCC phase plays a major role in determining its saturation magnetization. When the volume fraction change of BCC phase is not evident, the higher volume fraction of FCC phase will influence its magnetization at 2 T. Our present work might provide insights into analyzing the evolution of both mechanical and magnetic properties of HEAs caused by complex phase transformation.