Microstructural evolution, mechanical profile, and fracture morphology of aluminum matrix composites containing graphene nanoplatelets

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.