Achieving homogeneous distribution of high-content graphene in aluminum alloys via high-temperature cumulative shear deformation

Abstract

Homogeneous dispersion of high-content graphene nano-platelet (GNP) in metals is challenging due to the serious aggregation tendency of graphene. Traditional secondary processing such as extrusion usually has too limited shear strains to reach a desirable GNP dispersion state. Our previous work demonstrated that 1.0 vol% GNP/Al composite was successfully produced via multiple wire-drawing at ambient temperature. However, the fabrication of 5.0 vol% GNP/Al composite was not successful because of the limited cumulative shear strains. Here we described fully dispersed state of 5.0 vol% GNP in Al by hot-drawing at an elevated temperature 400 °C. The evolution of the microstructures and mechanical properties were investigated in relation to the number of drawing passes. The ultra-fine grains with size 372 nm were obtained via dynamic recrystallization after drawing for six passes (cumulative strain 94%). In particular, stripping of the GNP into thin layers and their preferential alignment in the wire axis occurred during the shear deformation. As a result, 5.0 vol% GNP/Al composite produced by six-pass drawing possessed improved yield strength (σs, 449 MPa) and ultimate tensile strength (UTS, 461 MPa). The results demonstrated the feasibility of dispersing high-content GNP in aluminum alloys by extrusion followed by multi-pass hot drawing techniques.

Keywords

• Graphene nano-platelet (GNP)
• Aluminum matrix composites (AMCs)
• Hot extrusion
• Multi-pass hot drawing
• Mechanical properties