From design to performance: a critical review of in situ reinforced aluminum matrix composites

Recent advances in aerospace, automotive, and communication electronics have driven a growing demand for aluminum matrix composites (AMCs) with superior mechanical properties. The performance of AMCs is largely governed by their reinforcements, which typically feature high strength, melting point, and chemical stability. In particular, reinforcements formed via in situ chemical reactions offer distinct advantages over their ex situ counterparts, including cleaner interfaces, better thermodynamic compatibility, and more uniform dispersion within the matrix. This paper provides a comprehensive and critical review of the state-of-the-art in processing, properties, and applications of in situ reinforced AMCs. Emphasis is placed on various in situ synthesis strategies, elucidating the reaction mechanisms and characterization techniques associated with different precursor materials. It critically examines how key fabrication methods influence the control of reinforcement characteristics (e.g., size, distribution, and interfacial structure) and the evolution of microstructural features. The resultant impact on the overall composite performance is also systematically analyzed. Finally, based on current understanding, this review outlines key challenges and proposes future research directions for the development of in situ reinforced AMCs. By integrating advanced processing, microstructural design, in situ synthesis mechanisms, and performance strengthening into a multi‑dimensional framework, this review establishes clear linkages from material design and processing to microstructural evolution and final performance, thereby aiming to guide the rational design and development of high‑performance AMCs.