Graphene platelets reinforced aluminum matrix composite with enhanced strength by hot accumulative roll bonding

Abstract

Accumulative Roll Bonding(ARB) process was used to develop few-layer graphene nano platelets reinforced aluminum matrix (GNPs/Al) composite in the form of sheets. Annealed Al sheets were ARB processed up to 6 pass along with coating of graphene between stacked sheets in first and second pass. Another set was prepared with same process parameter in the absence of graphene coating. Properties of these two set of samples were analyzed on the basis of film theory of ARB process which enables micro-level mixing of material on stacked layer interface. Hence the problem of graphene agglomeration was overcome through our process. The Raman spectra at the cross-section was taken which not only show the strong interaction of GNPs with Al matrix due to increased D and D' band but also the graphene quality enhancement on the basis of single symmetric 2D band. Samples were then subjected to universal testing machine (UTM) and Vickers microhardness tester. Results showed up to ~73% increment in yield strength and ~27% increment in hardness of GNPs/Al matrix composite. Fracture surface of tensile specimen was further examined under SEM to understand the fracture mechanics at higher passes, which elucidate elongation variation and delamination behavior of stacked sheets. Deep elongated dimples with the smoothed surface in GNPs/Al composite are the cause of reduced elongation. But the final composite was having improved strength with appreciable ductility. The improvement was further justified by increment in dislocations, calculated using Williamson-Hall plot on X-ray diffraction (XRD) data. All results signify the effectiveness of the proposed technique for the development of GNPs/Al composite.