Synthesis of AA2024-(SiO2np+TiO2np) hybrid nanocomposite via stir casting process

In this study, AA2024-(X vol.% SiO2np + Y vol.% TiO2np) (X, Y = 0.5, 1.0) hybrid nanocomposites were fabricated the via stir casting process and their structural and mechanical properties were examined. The results indicated that the grain sizes of the hybrid nanocomposites were reduced by the addition of nanoparticles into the matrix alloy. The analysis of mechanical properties also showed an increase of about 30, 36 and 7% in the hardness, tensile strength, and tensile yield strength, respectively. In the larger amounts of nanoparticles, scanning electron microscopy studies showed that there were more quantities of nanoparticles agglomerates in the structure, reducing the mechanical properties of the nanocomposite with 1 vol.% of SiO2 nanoparticles, as compared to the nanocomposite with 0.5 vol.% of SiO2 nanoparticles. The main strengthening mechanisms were estimated to be Hall-Petch strengthening, Orowan strengthening, and the coefficient of thermal expansion mismatch and elastic modulus mismatch between the reinforcements and the metal matrix. There was also some evidence showing some of the singular and agglomerated nanoparticles in the matrix on the fractured surfaces of the nanocomposites.