Effect of MgO particles with in-situ graphene coating on mechanical and thermal expansion properties of aluminum matrix composites

Abstract

Easy agglomeration and poor interface are bottlenecks restricting the effective transfer of internal stress in ceramic nanoparticle-reinforced metal matrix composites (MMCs). In this study, nanosized MgO particles coated by in-situ few-layered graphene (MgO@FLG) were synthesized using methane as carbon source by chemical vapor deposition (CVD) method, then incorporated with Al matrix through powder metallurgy routes. It is demonstrated that MgO@FLG particles in composites were endowed with more significant strengthening contributions in comparison with the counterparts without coating. This is critically attributed to the interlayer van der Waals of FLG promoting the particle dispersion, and the chemical interface, which involves Mg-O-C bonding and moderate Al4C3 nanorods, improving the interfacial bonding. The thermal expansion behaviors and coefficient of thermal expansion (CTE) of composites were investigated by testing thermal cycling ranging from 50 to 400 °C. The hysteresis residual strain of MgO@FLG/Al composites is less than that of MgO/Al composites, indicating a robust interface adhesion to adapt to the changing of internal stress. Furthermore, a low experimental CTE value was obtained for the MgO@FLG/Al composite, and its theoretical CTE value falls into a possible prediction region of Kerner’s model. This work provides new insights into the reinforcement modification and interface design of particle-reinforced MMCs, facing the application of structural components with the improved thermal stability and high load-bearing capacity.