Enhancing strengthening efficiency of graphene nano-sheets in aluminum matrix composite by improving interface bonding

Abstract

Three 0.3 vol% graphene nano-sheet reinforced Al composites (GNS/Al), namely forged GNS/Al–4Cu, extruded GNS/Al–4Cu and forged GNS/Al–4Cu–1Mg, with different graphene-Al interfaces were prepared by wet mixing of graphene oxide aqueous solution and flaky Al powders, thermal reduction and subsequent powder metallurgy route. Their strengthening behaviors related with interface bonding were investigated, with the help of high resolution transmission electron microscopy, X-ray photoelectron spectroscopy and interface bonding test of specially designed model materials. In the forged composite, amorphous Al2O3 layer was observed between GNS and Al, resulting in a weak bonding of GNS and Al with interface shear strength of 117 MPa and normal strength of 227 MPa. In this case, nearly no strengthening effect was achieved by GNS addition. Using extruding to replace forging or adding Mg element could respectively break or exhaust amorphous Al2O3 layers, leading to improved graphene-Al interface bonding strength due to high fraction of Al–C ionic bond, thereby significantly increasing the strengthening effect of GNS. The best strengthening efficiency with a strengthening factor of ~33 was achieved in the forged GNS/Al–4Cu–1Mg due to strong interface shear strength of 209 MPa and normal strength of 402 MPa.