Hierarchical synergistic strengthening and wear resistance of a hypereutectic Al–20Si alloy via in-situ dual ceramic reinforcement

In this study, an Al–20Si matrix composite reinforced by in-situ formed dual ceramic phases (SiC and Al 2 O 3 ) was fabricated via ball milling, controlled oxidation, and powder metallurgy processing. Rod-like α-SiC particles and blocky θ-Al 2 O 3 particles are uniformly distributed within the aluminum matrix and exhibit strong metallurgical bonding with the Al phase. Owing to the in-situ dual-ceramic reinforcement, the composite exhibits a superior combination of mechanical and tribological properties, including an ultimate tensile strength of ∼352 MPa, a hardness of ∼140 HB, and a low wear rate of ∼2.5 × 10 -4 mm 3 /(N·m). Compared with the monolithic Al–20Si alloy, the tensile strength and hardness increase by approximately 79 % and 84 %, respectively, while the wear rate decreases by 40 %. Microstructural and subsurface analyses reveal that the enhanced performance originates from a hierarchical synergistic strengthening framework. Orowan strengthening provides the primary resistance to plastic deformation, geometrically necessary dislocation accumulation reinforces this resistance, and load transfer stabilizes deformation at larger length scales. Strong in-situ particle–matrix interfaces enable the cooperative activation of these mechanisms, suppress subsurface plastic deformation, and stabilize the tribological interface during sliding. These findings establish a strengthening–wear coupling framework, offering a mechanistic basis for designing wear-resistant hypereutectic Al–Si alloys.