Anisotropic thermal conductivity of aluminum matrix composites reinforced by graphene nanoplates and ZrB2 nanoparticles

This study investigates the anisotropic thermal conductivity of aluminum matrix composites reinforced with graphene and ZrB2 nanoparticles, while simultaneously maintaining high strength and high toughness. The discontinuous layered GNPs-ZrB2/AA6111 composite was prepared by using in-situ melt reactions and semi-solid stirring casting technology, combined with hot rolling deformation processing. Microstructure research reveals that the GNPs are aligned parallel to the RD-TD plane, whereas ZrB2 nanoparticles aggregate into cluster strips, collectively construct a discontinuous layered structure. The multilayer arrangement maximizes the in-plane thermal conductivity of GNPs. The tightly bonded GNPs/Al interfaces with the locking of CuAl2 nanoparticles ensure that the GNP fully use their high thermal conductivity. Therefore, the GNPs-ZrB2/AA6111 composite achieved high in-plane thermal conductivity (230 W/(m·K)), which is higher than that of the matrix (206 W/(m·K)). The improved in-plane thermal conductivity is primarily attributed to the exceptionally high intrinsic in-plane thermal conductivity of GNPs and their two-dimensional layered structure. However, the composite exhibits pronounced thermal conductivity anisotropy between the in-plane and through-plane directions. The reduced through-plane thermal conductivity is predominantly caused by the intrinsically low through-plane thermal conductivity of GNPs and the increased interfacial thermal resistance from additional grain boundaries.