Strengthening effect in aluminum-graphene nanolayered composites via interface engineering

Abstract

The exceptional stiffness of graphene has driven extensive research on its integration within metal-graphene multilayer (ML) composites to enhance mechanical properties. This study investigates the influence of interfacial characteristics on the mechanical performance of Aluminum-graphene (Al-Gr) ML composites, employing either amorphous Al₂O₃ or crystalline Ag as interlayers. Al-Al₂O₃-Gr ML exhibited limited strengthening, with transmission electron microscopy (TEM) analysis revealing that dislocations were predominantly impeded at the Al₂O₃ interface rather than the graphene interface, suggesting a negligible strengthening of graphene comparable to Al-Al₂O₃ ML. In contrast, Al-Ag-Gr ML with an epitaxial Al-Ag interface transmitting dislocations to the graphene displayed a substantial increase in strength, surpassing the strength of Al-Ag ML by more than 30 %. To further investigate these contrasting behaviors, molecular dynamics (MD) simulations were conducted, revealing that the strengthening contribution of graphene depends heavily on the deformation behavior of the Al₂O₃ layer. At small strains, where shear banding was absent in the Al₂O₃ layer, graphene provided negligible reinforcement. However, at larger strains, when shear banding initiated, graphene effectively restricted further plastic deformation, markedly enhancing strength. These findings highlight the crucial role of interfacial structure and associated deformation mechanism in governing the mechanical behavior of metal-graphene ML composites.