Investigating microstructure and mechanical properties of aluminum matrix reinforced-graphene nanosheets composites fabricated by mechanical milling and equal channel angular pressing

A few layer graphene reinforced metal matrix nanocomposites with excellent mechanical properties and low density are a new class of advanced materials for a broad range of applications. A facile three steps approach based on ultra-sonication for dispersion of graphene nanosheets (GNSs), ball milling for Al powder mixing with different GNSs weight percent and equal channel angular pressing for powders consolidation at 200°C, has been applied for nanocomposites fabrication. The Raman analysis revealed that the GNSs in the sample with 0.25 wt.% were exfoliated by the creation of some defects and disordering. X-ray diffraction and microstructural analysis confirmed that the interaction of GNSs and matrix was almost mechanical interfacial bonding. Density test demonstrated that all samples except 1 wt.% GNSs were fully densified due to the formation of microvoids, which was observed in scanning electron microscope analysis. Investigation of mechanical properties showed that by using Al powders with commercial purity, 0.25 wt.% sample possessed the maximum hardness, ultimate shear strength and uniform normal displacement in comparison with other samples. Highest mechanical properties which was observed in 0.25 wt.% GNSs composite, resulting from the embedding of exfoliated GNSs between Al powders, excellent mechanical bonding and grain refinement. Oppositely, agglomerated GNSs and existence of microvoids caused deterioration of mechanical properties in 1 wt.% sample