High-content graphene nanoplatelet reinforced aluminum composites produced by ball milling and hot extrusion

Due to the high specific surface area of graphene, the effective incorporation of high-content graphene in metals is challenging. Here, aluminum composites with graphene nanoplatelet (GNP) content up to 5.0 vol% were prepared by spark plasma sintering (SPS) of blended powders with various ball milling regimes and subsequent hot extrusion. The effects of GNP distribution state on the properties of GNP/Al composite were investigated. 5.0 vol% GNPs were uniformly dispersed in aluminum matrix by high-speed ball milling (HSBM) process, but with damage GNPs due to the too high energy input. By contrast, the wellstructured and dispersed GNPs in aluminum powders were obtained via shift-speed ball milling (SSBM). The clear GNP-Al interface in extruded SSBM composite was attributed to well-structured GNPs. As a result, the yield strength (YS) and ultimate tensile strength (UTS) of composite produced by SSBM reached 279 and 303 MPa, which are 166% and 116% higher than those of monolithic Al. This demonstrated that it may be promising to introduce high-content GNPs with tailorable interface in Al alloys via modified ball milling technique and hot extrusion.