The role of accumulative roll bonding after stir casting process to fabricate high-strength and nanostructured AA2024-(SiO2+TiO2) hybrid nanocomposite

Abstract

Major challenges in casting routes for the fabrication of metal matrix nanocomposites are the weak bonding between reinforcement and matrix, porosity and nonuniform distribution of nanoparticles in the matrix alloy following in the presence of agglomerated nanoparticles and reinforcing nanoparticle free zones. Applying accumulative roll bonding as a severe plastic deformation process can improve the microstructure of the matrix alloy and the distribution of reinforcing nanoparticles in the metal matrix after the production of the casting nanocomposite. In this study, the accumulative roll bonding process was used to complete the composite fabrication process on the as cast AA2024-(SiO2+TiO2) hybrid nanocomposites. The microstructural and mechanical examinations of the accumulative roll bonded hybrid nanocomposites were characterized by measurement of density using the Archimedean immersion method, optical metallography, field emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, and hardness and tensile tests. The results showed that the microstructure of the accumulative roll bonded hybrid nanocomposite had a great distribution of nanoparticles in the matrix without any significant porosity. In the final nanostructured hybrid nanocomposite, the grain size of 100 nm was obtained. Mechanical examinations also indicated that the hardness, ultimate tensile strength and yield stress of the nanocomposite increased as the number of accumulative roll bonding cycles increased. After five accumulative roll bonding cycles, hardness, ultimate tensile strength and yield stress values of the nanocomposite increased about 160%, 110% and 300% rather than those of non-accumulative roll bonded monolithic product, respectively.