Microstructure and Mechanical Properties of Aluminum: Graphene Composites Produced by Powder Metallurgical Method

Aluminum-based composites containing 0.1-0.7 wt.% graphene were produced by the powder metallurgical process. The microstructure of the nanocomposites was studied using LM, SEM, EDS, TEM, and XRD. A relatively uniform distribution of graphene nano-platelets and compacted agglomerates in composites with different graphene contents was found. A mechanical bond between the nano-platelets and the aluminum matrix was established. Under the conditions used, neither particles nor nanoparticles of Al4C3 are formed. The microhardness and mechanical properties were studied. It was found out they are the highest in the composite containing 0.1% graphene. The change of these properties with the graphene content increasing has the same character. Agglomeration of GNPs occurs in all composites containing graphene, but a part of GNPs remain in a dispersed, non-agglomerated state. The microhardness and mechanical properties depend on this part of individual GNPs. It was proven that the observed increase in the yield strength of the studied composites is due to Orowan's strengthening mechanism. The fracture mechanism of GNPs de-bonding and pull-out from the aluminum matrix of the composite was experimentally proved.