Microstructure transformation and mechanical properties of Co₆₈Al_xFe_24.7-xV_4.8Cr_2.5 high-entropy alloys with dual-phase structures

Here, we designed Co₆₈Al_xFe_24.7-xV_4.8Cr_2.5 (x = 16.5,17 and 18 at.%) high-entropy alloys (HEAs) by adjusting the atomic ratio of Fe and Al elements and successfully prepared a series of eutectic or near-eutectic HEAs by direct casting method. All designed HEAs exhibit a dual-phase eutectic or near-eutectic structure containing FCC and B2 phases. As the Al content increases from 16.5 to 18 at.%, the microstructure of the designed HEAs evolves from eutectic structure to hypereutectic structure. Among the studied HEAs, Co₆₈Al_16.5Fe_8.2V_4.8Cr_2.5 HEA with eutectic structure exhibits an excellent strength-plastic combination, i.e., the yield strength of 761 MPa, the ultimate compressive strength of 2178 MPa and the fracture strain of 21.9 %, respectively. Such an excellent mechanical performance is mainly attributed to dislocation strengthening and interface strengthening. Furthermore, the stable K-S orientation relationship between FCC and B2 phases endows this HEA with remarkable strength-ductility combination. The design strategy in this work can provide new ideas for the development of high-performance dual-phase HEAs. © 2024 Elsevier Inc.