Strengthening and Mechanical Properties of SiC and Graphite Reinforced Al6061 Hybrid Nanocomposites Processed Through Ultrasonically Assisted Casting Technique

Abstract

Al6061 alloy-based hybrid nanocomposites reinforced with 2wt% SiC and x wt% of graphite (x = 0, 0.5, 1, 1.5, 2 and 3) nanoparticles are fabricated through ultrasonically assisted casting technique. Microstructure, phases, grain size and fracture surfaces of the hybrid nanocomposites are studied to understand the mechanical properties. Microstructural studies revealed the uniform distribution of SiC and graphite nano-reinforcements in the matrix. The small-scale clusters appeared in the microstructure with the increase in graphite nanoparticles. The grain size, density, hardness and ultimate tensile strength of hybrid nanocomposites decreased with the rise of graphite in the composite material. The yield strength of the hybrid nanocomposites increased with increase in graphite up to 2 wt% and then decreased. SiC and graphite dual phase nanoparticles’ strengthening effect on yield strength was theoretically evaluated using various strengthening mechanisms including porosity effect. Enhancement of yield strength in hybrid nanocomposite due to strengthening mechanisms followed the trend $\Delta \sigma_{{\Delta {\text{CTE}}}} > \Delta \sigma_{\text{Orowan}} > \Delta \sigma_{\text{HP}} > \Delta \sigma_{\text{load}}$. The predicted yield strength of hybrid nanocomposites obtained using the modified Clyne model and quadratic summation model were close to the experimental values. Fracture surfaces of hybrid nanocomposites exhibited brittle fracture with interdendritic cracking, stepwise facets and particle pull out with the increase in graphite content in the matrix.