Effects of graphene nano particles on interfacial microstructure and mechanical properties of Al7150/B4C hybrid nanocomposite fabricated by novel double ultrasonic two stage stir casting technique.

In the present research, an Al7150 alloys-based hybrid nanocomposite was fabricated by incorporating boron carbide and graphene nanoparticles through a novel fabrication method of double ultrasonic two-stage stir casting. Initially, the Al-B 4 C nanocomposite was optimized based on better microstructural and mechanical properties, and then a hybrid nanocomposite was prepared by incorporating graphene nanoparticles into the optimized Al-B 4 C nanocomposite. Homogeneous dispersion of graphene and boron carbide nanoparticles in Al7150 matrix was successfully achieved due to the double ultrasonic effect analyzed by Field Emission Scanning Electron Microscopy (FESEM) and High Resolution Transmission Electron Microscopy (HRTEM) analysis. Significant dispersion of nanoreinforcements with enhanced interfacial bonding and dislocation strengthening improved the microstructural and mechanical properties of the Orovan reinforced hybrid nanocomposite. The Vickers microhardness and ultimate tensile strength were improved by 19 % and 47 %, respectively, for the optimized Al-B 4 C nanocomposite compared to base metal. However, the Vickers microhardness and ultimate tensile strength were significantly improved by 36 % and 57 %, respectively, for the optimized hybrid nanocomposite compared to the base material (BM). The hard AlB 2 , Al 3 BC and Al 4 C 3 phases are formed due to the reaction between the matrix and reinforcement during solidification and act as reinforcement within the matrix and resist dislocation movements, resulting in a significant improvement in the mechanical properties of the nanocomposite. Fractography analysis by SEM also confirms the enhanced bonding of graphene nanoparticles as it deforms/slips during fracture and supports the effect of double ultrasonication on the tearing of boron carbide nanoparticles. [Display omitted] • Homogeneous dispersion of graphene and boron carbide nanoparticles in Al7150 matrix. • Dislocation density, Hall-Petch relationship, and Orowan strengthening mechanisms play a dominant role. • Graphene nanoparticles control the grain boundary migration through the Zener pinning effect. • Intermetallic hard phases Al 4 C 3 , Al 3 BC and AlB 2 are significantly enhanced the properties. • Interconnected network of graphene slides during deformation and resist the fracture. [ABSTRACT FROM AUTHOR]