Microstructural evolution, mechanical profile, and fracture morphology of aluminum matrix composites containing graphene
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Rafi Ud-Din Materials Division, Pakistan Institute of Nuclear Science and Technology, Nilore 45650, Pakistan
Iftikhar Ahmad Deanship of Scientific Research, Advanced Manufacturing Institute, King Saud University, Riyadh 11421, Kingdom of Saudi Arabia
Tayyab Subhania) Composite Research Centre, Department of Materials Science and Engineering, Institute of Space Technology, Islamabad 44000, Pakistan (Received 9 January 2017; accepted 13 March 2017)
Aluminum matrix composites were prepared by powder processing route containing three different loadings of graphene nanoplatelets, i.e., 1 wt%, 3 wt%, and 5 wt%. Ball milling of composite powders was performed to ensure the uniform dispersion of nanoplatelets in aluminum powder, followed by their consolidation to near theoretical densities. Microstructural evolution after composite preparation was witnessed by X-ray diffraction, optical microscopy, and scanning electron microscopy, while the mechanical property profile was evaluated by hardness, compression, and flexural tests. The mechanical properties of composites containing 5 wt% nanoplatelets were found with maximum improvements in hardness, compression, and flexural strengths of 35%, 433%, and 283%, respectively. This increase in mechanical performance is related to uniform dispersion and microstructural development in composites by incorporating nanoplatelets. Fractographic characterization indicated a change in fracture morphology from matrix-dominant in pure aluminum to nanoplatelet-dominant in composites. In particular, shearing and pull out of nanoplatelets were observed during the fracture of composites with simultaneous restricted plastic deformation of the surrounding aluminum matrix.
I. INTRODUCTION
Aluminum matrix composites (AMCs) are widely used for aerospace and automobile applications due to their attractive mechanical properties.1 As a result, a variety of fibers and particles have been reinforced in aluminum and its alloys including metallic carbides,2 oxides,3 borides,4 and nitrides.5 Among reinforcements, carbon fibers have been extensively incorporated in AMCs due to their increased strength and stiffness.6 The recently emerged carbon-based nanomaterials, i.e., carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) are considered to provide better mechanical properties than their micrometer-sized cousins, i.e., carbon and graphite fibers.7 Therefore, CNTs and GNPs are highly attractive to prepare a novel class of composites containing Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.111
carbonaceous reinforcements at nanometer scale and initial investigations have provided promising results.8,9 However, the real translation of mechanical properties of CNTs and GNPs into nanocomposites has not yet been achieved. The issues related to the dispersion of CNTs and GNPs in the aluminum matrix, their consolidation to near theoretical densities, and in particular the control on the reinforcement–matrix interface are stil
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