  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.
