Investigation of the phase stabilities in AlNiCoCrFe high entropy alloys

High-entropy alloys (HEAs) are a developing class of materials that show great potential for a variety of commercial structural and coating applications, particularly where heat and corrosion resistance are desired. In these types of applications, the relative phase stabilities play a crucial role, since they influence the material design process and expected component lifetimes. However, a satisfactory understanding of the phase stabilities in HEAs and the ability to thermodynamically predict their behaviors is limited. This study methodically couples analytical characterization techniques with predictions based on CALPHAD models to investigate the phase equilibria and phase stabilities of a series of AlNiCoCrFe based HEAs. Heat treatments were conducted at 700 °C for 1000 h and 1050 °C for 520 h, followed by water quenching, to ensure adequate time for metastable equilibrium to be achieved. The accuracy and merit of the thermodynamic simulations in predicting the stable phases and their respective chemistries is discussed relative to the experimental observations.