A novel Co-free Al0.75CrFeNi eutectic high entropy alloy with superior mechanical properties

Eutectic high entropy alloys (EHEAs) with superior mechanical properties and good castability are one of the most promising candidates among high entropy alloys (HEAs) for engineering applications. In this study, a new Co-free Al0.75CrFeNi EHEA with a low density of ~ 6.56 g/cm3 was designed and prepared, the solidification process and ambient deformation behavior of the alloy were investigated in detail. Al0.75CrFeNi was composed of a disordered body-centered cubic (BCC) phase and an ordered body-centered cubic (B2) phase, which grew alternately to form a beautiful sunflower-like eutectic morphology. The alloy exhibited excellent mechanical properties with a high yield strength (σ0.2) of 1482 ± 56 MPa, fracture strength (σbc) of 3639 ± 190 MPa, and elongation to fracture of ~37.8% ± 1.5%. The high strength and low density of the alloy lead to a superior specific yield strength of ~ 226 KPa•m3/kg. During deformation, dislocation gliding in the BCC phase dominated the plastic deformation in the early stage. Subsequently, the dislocation activated in the B2 phase when the strain was further increased. Dislocation interactions and microstructural features, such as grain boundaries and substructures, in different stages generated the good balance between the strength and the ductility of the alloy.