Microstructure and mechanical properties of L12-strengthened CoFeMnNiMo0.2Alx high-entropy alloys

Developing alloys with excellent strength-ductility combination is urged desirable for advanced structural application. However, it still remains challenging in spite of years' efforts. Face centered cubic (FCC) high -entropy alloys (HEAs) commonly exhibit superb ductility. However, the low strength and hardness would limit the development of the FCC-structured materials. Here, the FCC + L12 + BCC structured CoFeMnNi-Mo0.2Alx were designed and prepared. The CoFeMnNiMo0.2Al0.5 HEA displays outstanding compressive prop-erties, whose ultra-high compressive strength is 1900 MPa and the fracture strain is 39.6%. The nano-hardness of the CoFeMnNiMo0.2Al0.5 HEA is nearly 8 GPa. Moreover, the relationship between phase evolution, mechanical property, strengthening mechanism, and Mo, Al concentration are systematically discussed. These findings will shed light on exploring novel HEA systems with high performance for future usage.