On the correlation between L12 nanoparticles and mechanical properties of (NiCo)52+2x(AlTi)4+2xFe29-4xCr15 (x=0-4) high-entropy alloys

Abstracts Different L12-Ni3(Ti, Al) phase contents in (NiCo)52+2x(AlTi)4+2xFe29-4xCr15 (x = 0-4) high-entropy alloys are designed based on CALPHAD and its effects on mechanical properties are systematically studied. Results show that excellent combination of yield strength (635-753 MPa), ultimate tensile strength (1010-1074 MPa), and fracture strain (23-31%) could be obtained for high-entropy alloys (x = 2 and 3). Almost half of the yield strength comes from nano-sized L12-type precipitates strengthening. The yield strength experienced sharp increment and the ductility showed an obvious decrease when the precipitated L12 phase increased in the range 0–14.2 wt%, with corresponding Al and Ti concentrations in the range of x = 0-3. Furthermore, when the precipitated L12 phase exceeds 14.2 wt%, merely a slight increment in yield strength was observed, but the fracture strain declined to around 13%. The present results contribute to understanding the strengthening mechanisms of L12-strengthened HEAs and may provide some reference for its application.