Microstructural evolution and mechanical properties of Al_0.25CrFeNiTi_0.25 high-entropy alloy prepared by mechanical alloying and spark plasma sintering

Achieving an excellent strength-ductility synergy in high-entropy alloys (HEAs) remains a significant challenge. In this study, Al_0.25CrFeNiTi_0.25 HEA powders were fabricated by mechanical alloying (MA) with 1 wt% stearic acid as a process control agent (PCA), followed by densification via spark plasma sintering (SPS). This work systematically investigated the formation mechanism of alloying powders during MA, focusing on the effects of PCA on powder morphological evolution, elemental distribution uniformity. The PCA was instrumental in refining the powder morphology, resulting in a final crystallite size of 7.61 nm. Furthermore, the alloy powder exhibited remarkable thermal stability, retaining a stable dual-phase structure upon heating above 910 °C. After SPS at 1100 °C, the bulk alloy demonstrated outstanding mechanical properties with a yield strength of 1518.67 ± 28.16 MPa, an ultimate compressive strength of 2910.67 ± 63.06 MPa, and a fracture strain of 40.33 % at room temperature. Microstructural analysis revealed that the in-situ formed TiC particles, with a volume fraction of 6.51 %, contributed a considerable Orowan strengthening increment of 105.20 MPa. This study thereby proposes a viable strategy for the preparation and performance enhancement of high-entropy alloys.