Engineering L1₂ precipitate and intergranular B2 phase for simultaneous high-temperature strength and fracture resistance in FCC/B2 high-entropy alloys

FCC/B2 dual-phase high-entropy alloys (DHEAs) exhibit great potential for high-temperature applications due to their unique combination of low density, excellent mechanical properties, and good oxidation resistance. However, achieving an optimal strength-ductility balance at elevated temperatures remains a challenge. In this study, the dual-phase and precipitation structures of FCC/B2 DHEAs were systematically tailored by varying the Ni/Co content. It was found that an increased Ni/Co ratio resulted in a lower fraction of the B2 phase and promoted L1₂ precipitation within both the FCC and B2 phases. The optimized microstructure was featured by a balanced combination of dual-phase matrix and high-density precipitates. At 800 °C, the increased volume fraction of L1₂ precipitates improved the yield strength, while the retained B2 phase effectively suppressed intergranular cracking, thereby preserving ductility. These findings offer a practical strategy for designing low-density, high-performance FCC/B2 DHEAs for future high-temperature structural applications.