Interface Engineering and Microstructural Enhancement of Aluminum LM25 Composites Reinforced with MoS 2 and SiC Nanoparticles

This study addresses challenges in metal matrix composite fabrication by optimizing an ultrasonic-assisted stir casting process for aluminum LM25 composites reinforced with 5 wt% MoS₂ and varying SiC nanoparticles (5–15 wt%). While previous research explored individual benefits of these reinforcements, their synergistic effects in hybrid composites remain underexplored. Our experimental investigation establishes correlations between processing parameters, microstructure, and mechanical properties. SEM–EDX mapping confirms uniform reinforcement dispersion with well-defined interfacial reaction zones (120–180 nm). Porosity decreases from 3.2% in the unreinforced alloy to 1.1% in the 15 wt% SiC composite. The LM25–5% MoS₂–15% SiC composite demonstrates significant mechanical improvements: 34.23% higher ultimate tensile strength (312.64 MPa), 40.93% increased yield strength (220.56 MPa), and 40.57% greater hardness (118.24 BHN). These enhancements result from multiple strengthening mechanisms including Orowan strengthening, Hall–Petch effect (grain size reduction from 42 to 12 μm), and improved load transfer efficiency. Fractography reveals a transition from dimple-dominated ductile fracture in the base alloy to mixed-mode fracture with transgranular cleavage in reinforced composites.