Effect of Graphene Nanoplatelets Fillers on Mechanical Properties and Microstructure of Cast Aluminum Matrix Composites

Abstract

Recently, many studies on the production of graphite/graphene reinforced aluminum-matrix composites using different fabrication methods, such as powder or semi-powder method, have been performed. However, cast aluminum/graphite or aluminum/graphene composites have not been widely investigated and the research on this production method mainly focuses on 3D graphite particle reinforcements. In this study, the use of a 2D graphene structure, i.e. graphene nanoplatelets (GNPs), in the production of cast Al/GNP composites is investigated. Graphene nanoplatelets reinforced cast aluminum matrix composites were produced using aluminum alloy as matrix material and different graphene nanoplatelets contents. Specimens were cast into a heated rectangular steel mold, the temperature of which was 100°C. All specimens underwent tensile and bending tests as well as hardness measurements and microstructural investigation. Ultimate Tensile Strength (UTS) was considerably increased, simultaneously with a slight decrease of elongation at break, in the case of 0.1 wt% graphene nanoplatelets addition. Regarding bending performance, a slight increase was observed as well. The flexural behavior for 0.1 wt% graphene nanoplatelets addition was exactly the same with the matrix material. The graphene nanoplatelets content found to affect both the surface and the chemical composition of the interdendritic region. After 0.1 wt%, further increase of the wt% graphene nanoplatelets content lead to formation of aluminum carbides (Al4C3) at the grain boundaries, with a consequent drop on the mechanical performance of the Al/GNPs composite.