Strengthening CoCrFeNi high-entropy alloy by Laves and boride phases

Abstract

To strengthen the face-centered-cubic (FCC) type CoCrFeNi high-entropy alloy (HEA) by in-situ reinforced phase, (CoCrFeNi) 100-x (NbB 2 ) x (x=0, 2, 4, 6, 8, at.%) alloys were prepared. Phase constitution, microstructure, tensile mechanical properties of the alloys were studied, and the mechanisms were discussed. Results show that the microstructure of all the reinforced alloys consists of the matrix FCC phase, Laves phase, and (Cr 3 Fe)B x phase. The eutectic structure and (Cr 3 Fe)B x phases are formed in the interdendritic region, and the eutectic structure is composed of Laves and FCC phases. When x increases from 0 to 8, i.e., with increase of Nb and B elements, the volume fraction of Laves and (Cr 3 Fe)B x phases increases gradually from 0 to 5.84% and 8.3%, respectively. Tensile testing results show that the ultimate strength of the alloys increases gradually from 409 MPa to 658 MPa, while the fracture strain decreases from 75% to 1.6%. Fracture analysis shows that the crack originates from the (Cr 3 Fe)B x phase. The CoCrFeNi alloys are mainly strengthened by the second phase (Laves phase and boride phase).

Evaluation of Tribological and Electrochemical Properties of Multiphase CoCuFeNiNb High Entropy Alloy

“…On the other hand, the addition of Nb in high-entropy alloys (HEAs) has a significant impact on the formation of Laves phases. Research has shown that Nb can promote the formation of Laves phases in various HEAs, such as CoCrFeNi and CoCrFeMnNi alloys (Chen et al, 2022). The presence of Nb-rich Laves phases in these alloys contributes to strengthening mechanisms, enhancing the overall mechanical properties of the materials.…”