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 ℃ and 1200 ℃,respectively.Such volume fraction changes ofσ,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.