Process-structure-property studies on synergetic effect of contact and non-contact ultrasonication in AA5083-based bulk nanocomposite

High strength-to-weight ratio materials such as Al- and Mg-based nanocomposites have gained growing interest in engineering applications for aerospace, automotive, marine, energy, and military. This unabated demand can be met with the advent in materials science and processing technologies. The current study demonstrates a recently developed the technique that consists of the synergetic effect of contact and non-contact ultrasonication of liquid melt for dispersing nano-sized Al₂O₃ reinforcements in AA5083 alloy matrix. The work is primarily focused on the effects of two-step ultrasonication on wettability, dispersion of the nano-reinforcements in the AA5083 alloy matrix, and the resultant strengthening. The resultant is the AA5083–1 wt-% Al₂O₃ bulk nanocomposite, a high strength-to-weight ratio material. The extensive microstructure analysis comprising scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS) mappings reveals the uniform dispersion of nano-particles in different phases of the matrix. The electron back scattered diffraction (EBSD) studies confirm the grain refinement while the X-ray diffraction (XRD) identifies the various phases formed are determined using XRD. The achieved uniform dispersion in the nanocomposite is explicated based on the enhanced wettability due to the presence of Mg in the alloy, preheating of nano-particles, and the synergetic effect of contact and non-contact ultrasonication that avoids the formation of zones of lower cooling rates resulting in powerful micro-convection. The resultant enhancement in the mechanical properties is explained based on available strengthening mechanisms. A comprehensive discussion on process-structure-property correlation has been presented.