Synergic Effects of Interfacial Compounds and Strengthening Mechanisms in Enhancing Mechanical Strength of Al-B₄C-GNPs Hybrid Nanocomposite

In this study, Al7150-B₄C-graphene hybrid nanocomposite, widely used in structural aircraft components due to its high strength and wear properties, was successfully fabricated by novel double ultrasonic two-stage stir casting. A significant enhancement of the strengthening effect on the tensile strength of the hybrid nanocomposites due to the uniform dispersion and strong interfacial compounds of the matrix and nanoreinforcements was observed by field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) analysis. The ultimate tensile strength was significantly improved by 57% for the 0.3ABG hybrid nanocomposite than base material (BM). Different strengthening mechanism was studied and the increase in yield strength of the hybrid nanocomposite was calculated. The load transfer (~ 58%), mismatched coefficient of thermal expansion (CTE) (~ 17%), and Orowan (~ 14%) strengthening mechanisms were dominant to strengthen the hybrid nanocomposite. Graphene nanoparticles play a significant role in load transfer and mismatch CTE reinforcement due to excellent load-bearing capacity and negative CTE of graphene. The intermetallic compounds Al₄C₃, AlZn and Cu₂Zn₅, formed in composite and nano reinforcements have an extensive effect on load transmission from the Al7150 matrix to the nanoreinforcements. Finally, the importance of all strengthening mechanisms of hybrid nanocomposites is included in the various theoretical models presented to predict the yield strength of aluminum alloys-based nanocomposites.