Ball Milling-Assisted Stir Casting of Aluminum Composites with Progressive Synergistic Reinforcement of Al2O3, Si3N4 and TiC

Each reinforcement uniquely influences the matrix by imparting distinct properties. This study evaluates the use of aluminum oxide (Al 2 O 3 ), silicon nitride (Si 3 N 4 ) and titanium carbide (TiC) in an aluminum metal matrix composite (MMC) fabricated through a hybrid technique combining ball milling and stir casting. Initially, Al 2 O 3 is progressively incorporated into the matrix melt at uniform intervals of 0.5 wt.% until a threshold is reached. Subsequently, Si 3 N 4 is added to the established Al 2 O 3 threshold to determine its limit. Finally, TiC is introduced at the threshold levels of Al 2 O 3 and Si 3 N 4 to develop a composite that integrates the benefits of all three reinforcements. Experimental findings indicate that the optimal composition, achieving the highest ultimate tensile strength (UTS) of 117 MPa, consists of 1 wt.% Al 2 O 3 , 1 wt.% Si 3 N 4 and 0.5 wt.% TiC. This is 32.95% higher than that of the composite without any reinforcement. With this optimal composition, the Brinell hardness number (BHN) achieved is 51, showcasing a 29.1% improvement over composite without any reinforcements. The sample with the optimal composition also had a 66.91% improvement in ductility. Field emission scanning electron microscopy (FESEM) micrograph analysis, followed by electron backscatter diffraction (EBSD)-based grain size evaluation, confirms the viability of the Orowan and Hall–Petch strengthening mechanisms in the cast aluminum composite.