Effect of B Content on Microstructure and Properties of CrFeNiAlSi High-Entropy Alloys

A series of CrFeNiAlSiB (x = 0.1, 0.3, 0.5, and 0.7) high-entropy alloys (HEAs) were proposed by vacuum arc melting. The study aimed to investigate the effect of boron (B) content on the microstructure evolution, phase formation regulation, wear, corrosion, and oxidation properties. The results show that the CrFeNiAlSiB HEAs consisted of the BCC phase, (Cr, Fe)₃Si phase, and (Cr, Fe)B compound. The HEAs had a dendritic morphology, with silicon-rich phases between the grains and AlNi phases within the grains, and B forms a needle-like second phase with Cr elements. The hardness of the HEAs was mainly strengthened by the second phase, with B_0.3 HEA having the highest hardness of 1121 HV and the lowest wear per unit area of 0.97 mg·cm^-2. In a 3.5 wt % NaCl solution, B_0.3 HEA had the best corrosion resistance, with an annual corrosion rate of 0.043 mm/a. The increase of B content changed the second phase from the dispersed fine needle-like structure to the coarse flat noodles structure, which accelerates intergranular corrosion. The B element improved the high-temperature oxidation resistance of the alloy, reduced the oxidation rate of the alloy, and shortened the time for the HEAs to form a complete antioxidation film.