Influence of GNP Additions on the Microstructure, Mechanical Properties, and Electrical Conductivity of Cast A319 Aluminum Alloy

Aluminum metal matrix composites have gained increased interest in the automotive industry due to their high strength and thermal properties. In this research, the mechanical properties and electrical conductivity of A319 Al alloy castings with graphene additions (0, 0.05, 0.1, and 0.2 wt% additions) were investigated. The castings were carried out using hybrid semi-solid stirring and ultrasonic melt processing. The microstructure was analyzed using optical microscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy. The mechanical properties and electrical conductivity were measured via ambient temperature tensile testing and an eddy current tester, respectively. Graphene nanoplatelet additions (GNPs) effectively reduced the grain size and transformed the grains from a coarse and dendritic morphology to fine globular with improved distribution. Additionally, graphene was found to promote a reduction in Fe impurities, thereby reducing the presence of clusters of deleterious Al15(Fe, Mn)3Si2 Fe-bearing intermetallics. The tensile testing results exhibited improvements in the ultimate tensile strength (from 190 to 218 MPa) and yield strength (89-124 MPa) with graphene additions, while simultaneously maintaining good ductility (3.1-4.1%). Further, the A319/graphene composites exhibited improved electrical conductivity from 27 to 30.2% IACS. This research elucidates the mechanisms enhancing the strength and conductivity of A319 via graphene additions.