Microstructural evolution, mechanical and physical properties of graphene reinforced aluminum composites fabricated via powder metallurgy

Tremendous interest in graphene as reinforcement of metal matrix is drawn due to its excellent mechanical properties coupled with outstanding thermal and electrical properties. 0.5 wt% graphene nanoplatelets (GNPs) reinforced pure Al composites were fabricated by powder metallurgy. Effects of microstructure on both mechanical and physical properties are analyzed systematically. GNPs were thoroughly flattened after mechanical stirring. The Raman spectroscopy results of GNPs confirmed the defect repairing during composite powders preparation. After hot extrusion, the scanning electron microscope results presented that GNPs distributed uniformly in Al matrix. Aluminum carbide was found on GNPs/Al interface via high-resolution transmission electron microscopy and partial reaction between Al and GNPs was also certified. The hardness, tensile yield strength and fracture strain of composite are 73 HV, 248 MPa and 16%, respectively. And the tensile yield strength is 65% higher than pure Al. The contribution ratios of grain boundary strengthening, load transfer effect and thermal mismatch mechanism are calculated as 42%, 56% and 2%, respectively. Thermal conductivity and electrical conductivity of composite were detected to be 201 W m(-1) K-1 and 56 %IACS. The reduction percentages are 2.4% and 6.7% compared with pure Al under the same procedure. Therefore, the insignificant loss of physical properties brought about exciting improvement on strength in return.