Design strategy for high-entropy alloys with enhanced microstructural stability and mechanical properties for high-temperature applications

The use of AlCoCrFeNi high-entropy alloy as high-temperature structural materials is limited because of their phase instability. To address this, we designed Co-free Al-Cr-Fe-Ni alloys with spinodal structures composed of disordered body-centered cubic (BCC) (A2) and ordered BCC (B2) phases. The effect of Al and Ni content on the phase fractions and that of the Cr content on the microstructure and B2 precipitate size were evaluated. The composition of the alloy was optimized to enhance its microstructural stability and room-temperature machinability. Finally, Al13.6Cr(x)Fe(75.2-x)Ni11.2 alloys were designed and investigated for their phase stability and mechanical properties at both ambient and elevated temperatures. The fabricated Al13.6Cr(x)Fe(75.2-x)Ni11.2 alloys exhibited adequate phase stability at high temperatures. Particularly, as the Al13.6Cr13.3Fe61.9Ni11.2 (13Cr) alloy exhibited ductility of 1.3 % at 298 K, it can be a potential candidate as a high-temperature structural material. These findings suggest a promising design strategy for high-entropy alloys.