Laser shock peening of nanocarbon–metal composites: Microstructural mechanisms, property enhancement, and processing windows

Laser shock peening (LSP) has attracted growing attention as a post-processing technique for tailoring the microstructure and reinforcement architecture of nanocarbon–metal composites based on lightweight aluminum and magnesium matrices. This review critically examines the influence of key shock-processing parameters, including peak pressure, strain rate, pulse duration, and temperature, on the microstructural evolution and resulting property enhancement in these hybrid systems. Particular emphasis is placed on the mechanisms by which LSP-induced plastic deformation, including grain refinement, dislocation generation, and deformation twinning, interacts with nanocarbon reinforcements to promote dispersion, partial alignment, and the formation of three-dimensional interconnected networks. The roles of graphene and carbon nanotubes as stress concentrators and defect-stabilizing agents are discussed in the context of interfacial strengthening and thermomechanical stability. Current evidence indicates that optimized LSP conditions can yield substantial improvements in hardness, wear resistance, fatigue life, and thermal transport anisotropy at low nanocarbon loadings, while preserving reinforcement structural integrity. Challenges related to scalability, process uniformity, and real-time characterization of shock–reinforcement interactions are identified. Emerging directions, including in situ diagnostics, additive manufacturing integration, and machine-learning-assisted process optimization, are discussed as pathways toward industrial implementation of LSP-architectured nanocarbon–metal hybrids.