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The University of Southampton

Research project: Manufacturing of graphene based aluminium metal matrix composites by high pressure torsion

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Currently available methods of making graphene-based aluminium alloy matrix composites (Gr AA 7075 MMC) result in carbide formation and reduction of graphene quality due to high temperature and solvents used in processing. To overcome these issues, a novel method to make Gr AA 7075 MMC using severe plastic deformation (SPD) is tested. The potential of graphene to improve the strength of aluminium alloy is experimentally studied

A relatively new approach of solid mixing to make graphene-based aluminium alloy matrix composites (Gr AA 7075 MMC) using severe plastic deformation (SPD) is tested. Variations in concentration of graphene nanosheets, and HPT process parameters are applied to optimise the fabrication route. The samples were studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X ray diffraction (XRD) line broadening analysis, which revealed the dislocation density and the crystallite size. XRD line broadening revealed a crystallite size of 28 nm for the 1 wt.% Gr AA 7075 MMC after 50 turns of HPT on which illustrates the capacity of HPT to produce a truly nanostructured material. Porosity evolution in the Al matrix during early stages of HPT was analysed.  The hardness of the material improved up to 300 % by HPT with respect to (w.r.t.) annealed bulk AA 7075 to reach a maximum hardness of 310 HV for the 0.5 wt. % Gr AA 7075 MMC processed by 20 turns of HPT. In contrast to cast and solution treated AA 7075, no consistent improvement in hardness is recorded in HPT processed AA 7075 due to artificial ageing.

The project is funded by High Commission of India.

High Pressure Torsion (HPT)
Overview of HPT Project

Associated research themes

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