Microstructure and properties of CoCrFeNiAlx (x = 0.1, 0.5, 1) high-entropy alloys enhanced by laser surface remelting

Abstract

In this study, CoCrFeNiAlx (x = 0.1, 0.5, 1) high-entropy alloys (HEAs) are prepared using vacuum arc melting. In order to improve the surface properties of CoCrFeNiAlx HEAs, their microstructure is manipulated by laser surface remelting (LSM). The microstructure, the mechanical properties, and the corrosion resistance of the HEAs before and after LSM are studied systematically. The microstructural analysis reveals that the LSM-samples contained either a single FCC phase (CoCrFeNiAl0.1 and CoCrFeNiAl0.5) or a mixture of BCC + B2 phases (CoCrFeNiAl1) with refined grains. Moreover, BCC precipitates and a spherical nano-dispersed phase (B2) are detected in the surface layer of CoCrFeNiAl0.5 and CoCrFeNiAl1, respectively. The mechanical properties of CoCrFeNiAlx alloys are found to be significantly enhanced after LSM, which is mainly ascribed to the generation of the BCC phase, dislocation reinforcement and grain-strengthening as well as precipitation hardening. The electrochemical measurements confirm that all samples (after LSM) have a positive potential and a lower current density in 3.5 wt% NaCl solution compared to the untreated sample. The results indicate that LSM can help homogenize the structure and improve the properties of CoCrFeNiAlx HEAs.