Effect of Fe/Ni Ratio on the Microstructure and Mechanical Properties of AlCr1.6FexNi(3.2−x)Si0.2 High-Entropy Alloys

AlCrFeNi-based high-entropy alloys (HEAs) have attracted considerable interest owing to their adjustable phase constitution and attractive mechanical performance. In this study, AlCr1.6FexNi(3.2−x)Si0.2 HEAs (x = 1.0–2.0) were fabricated by vacuum arc melting to systematically evaluate the influence of the Fe/Ni ratio on phase evolution, microstructural characteristics, and mechanical behavior. The results indicate that, with increasing Fe content, the phase constitution gradually changes from BCC+B2+σ to BCC+B2. Correspondingly, the microstructure evolves from floral and cellular eutectic morphologies to branch-like BCC-rich regions with inter-branch/intercellular eutectic constituents. At the same time, the Vickers hardness decreases from 584.1 HV to 365.7 HV as the Fe content increases. Compression results show a gradual reduction in alloy strength, whereas the deformation ability is noticeably improved. Fracture surface analysis further reveals that the alloys with x ≤ 1.4 exhibit typical brittle fracture features, while those with x ≥ 1.6 display incomplete fracture and enhanced plastic deformation. These results clarify the relationship among Fe/Ni ratio, phase constitution, microstructural evolution, and mechanical properties in AlCrFeNiSi-based HEAs.