Microstructural Evolution and Densification Behavior of Ball-Milled AlFeCoNi Medium-Entropy Alloy Consolidated by Conventional Sintering

This study investigated the synthesis and microstructural evolution of AlFeCoNi medium-entropy alloy powder processed by ball milling, conventional uniaxial pressing, and vacuum sintering at 900 °C for 1 h. The mechanically milled powder exhibited a refined, irregular particle morphology with a broad size distribution, indicating extensive fracture and cold-welding during milling. SEM (scanning electron microscopy) and EDS (energy-dispersive spectroscopy) observations showed effective elemental mixing of Al, Fe, Co, and Ni, with only limited evidence of large-scale segregation, suggesting that mechanical alloying promoted compositional homogenization. After compaction and sintering, the powder compact exhibited noticeable changes in microstructural continuity and pore morphology, indicating further microstructural evolution during thermal treatment. Overall, the results demonstrate the microstructural evolution of AlFeCoNi MEA during ball milling and subsequent conventional sintering, while further investigation involving quantitative densification measurements and optimization of sintering conditions is required to establish the consolidation behavior and microstructural uniformity of the alloy.