Deformation mechanism of the interfacial microregion in the 6H–SiC(0001)/Al(111) composite configuration

This study investigates the micromechanical behavior of the reinforcement/matrix interface in aluminum matrix composites under mechanical loading, with the aim of clarifying the interfacial strengthening mechanism. SiC particle-reinforced 2024 Al matrix composites were fabricated using a vacuum hot-press sintering process. Comprehensive microstructural characterization revealed the crystallographic orientation relationship at the SiC/Al interface. Molecular dynamics (MD) simulations were employed to systematically investigate the microscopic deformation mechanisms of the low-index 6H-SiC(0001)/Al(111) interfacial configuration under tensile loading normal to the interface. The stress-strain response and dislocation evolution show that the interfacial bonding exhibits a high yield strength, along with significant sustained plasticity and excellent load-bearing capacity after yielding. Plastic deformation is primarily governed by the formation and interaction of stair-rod dislocations, with a limited number of Shockley partial dislocations also observed. Atomic-scale structural evolution reveals the formation of a distinctive triangular-pyramidal L-C dislocation lock within the interfacial region, consisting of three immobile stair-rod dislocations linked by three stacking faults. This unique geometric configuration provides enhanced structural stability compared with conventional L-C locks and remains effectively pinned at the interface, serving as a physical barrier to crack propagation and thereby promoting ductile fracture behavior in the composite. Furthermore, crack nucleation and propagation tend to initiate within the near-interface region of the aluminum matrix adjacent to the Al-Si interface. Overall, this study clarifies the interfacial strengthening mechanism and identifies a stable dislocation lock structure at the 6H-SiC(0001)/Al(111) interface, providing guidance for the design of high-performance metal matrix composites.