Nanostructured red mud reinforced AlCoCrFeTi high-entropy alloys: Phase stabilization, microstructural evolution, and mechanical properties

The present study reports the synthesis and characterization of nanostructured red mud (RM) particle–reinforced Equi atomic AlCoCrFeTi high-entropy alloys (HEAs). Elemental powders were mechanically alloyed for 30 h in a high energy ball mill and the powders reduced to 8 nm was consolidated by vacuum hot pressing, and the resulting phases and microstructures were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD revealed progressive reduction in elemental peaks with milling time, leading to the formation of a nanocrystalline body-centered cubic (BCC) solid solution after extended milling. The base HEA without reinforcement exhibited multiple ordered phases, including B2 (BCC) and L1₂ (FCC), along with a brittle σ-phase arising from Cr- and Co-rich segregation. Upon the incorporation of RM, the B2 matrix phase was stabilized, while the intensity of σ-phase reflections decreased significantly. The presence of finely dispersed oxide-rich particulates from RM further contributed to dispersion strengthening and microstructural refinement. Mechanical testing demonstrated improved hardness, yield strength, and tensile strength with RM addition, achieving optimum performance at 4 wt% reinforcement. The tensile strength and yield strength were increased by 22% and 32% respectively for the HEA with 4% of RM reinforcement. Beyond this level, particle clustering and porosity led to strength reduction and loss of ductility. These results highlight the dual advantage of using RM as a sustainable reinforcement—enhancing the structural and mechanical performance of HEAs while simultaneously valorizing an abundant industrial by-product. The findings establish RM–reinforced HEAs as a promising class of high-performance and environmentally sustainable structural materials.