Ultrasonic Cavitation-Based Nanomanufacturing of Bulk Aluminum Matrix Nanocomposites

Abstract

Lightweight metal matrix nanocomposites (MMNCs) (metal matrix with nanosized ceramic particles) can be of significance for automobile, aerospace, and numerous other applications. It would be advantageous to develop effective nanomanufacturing methods for fabrication of bulk components of aluminum-based MMNCs through solidification processing. However, it is extremely difficult to disperse nanosized ceramic particles uniformly in molten aluminum. In this paper, a high power ultrasonic probe is used to disperse nanosized SiC particles into molten aluminum alloy A356. Experimental results show that the ultrasonic cavitation based dispersion of nanoparticles in molten aluminum alloy is effective. The uniform nanoparticle dispersion in the Al alloy matrix resulted in significantly improved mechanical properties. To enhance the nanomanufacturing efficiency, various nanoparticle feeding techniques were explored and experimental results are presented.

Strong, Ductile Magnesium-Zinc Nanocomposites

“…Current solidification processing methods for MMNCs are limited in size and geometric complexity, preventing designers from achieving the design flexibility desired for complex structures (e.g., engine blocks). Recently, Lan et al [11] and Yang et al [12,13] developed a new technique that combined solidification processing (e.g., casting) with an ultrasonic cavitation based dispersion of nanoparticles in metal melts. Nanoparticle reinforced magnesium and aluminum alloys were successfully fabricated.…”

“…Experimental results show a nearly uniform distribution and good dispersion of the SiC nanoparticles within the metal matrix, resulting in significantly improved mechanical strength while maintaining useful ductility. [11][12][13] It was reported [14] that ultrasonic cavitation can produce transient (in the order of nanoseconds) micro ''hot spots'' that can have temperatures of about 5000°C, pressures above 100 MPa, and heating and cooling rates above 10 10°C /s. The locally extreme conditions induced by the ultrasound can effectively disperse nanoparticles into molten metals due to the strong impact during cavitation and enhanced nanoparticle wettability.…”

Thixoforming of A356/SiC and A356/TiB2 Nanocomposites Fabricated by a Combination of Green Compact Nanoparticle Incorporation and Ultrasonic Treatment of the Melted Compact

“…In some previous work, [5,16] this was not the case, but other workers [44,45] did find same improvement. Figure 11 shows that nanoparticles enhance the formation of spheroidal eutectic (note the needle-shaped Si particles in the eutectic in Figure 11(b) vs the more spheroidal eutectic microstructure in Figures 11(c) and (d)).…”

“…[5] However, it has been shown that good dispersion of ceramic nanoparticles in molten metals is possible with the ultrasonic method due to high intensity ultrasonic waves with localized implosive impact, namely transient cavitation, and acoustic streaming. [15][16][17] It has been assumed that ultrasonic cavitation could break up nanoparticle clusters due to the collapse of cavitation bubbles when they reach a critical size in the clusters. [18] Acoustic streaming which is a circulating flow is then considered to play a role for distributing nanoparticles throughout the matrix.…”

“…[20][21][22] Several nanoparticle feeding mechanisms including a manual nanoparticle feeding from the top of the melt, [16] crucible placement approach, [23] double capsulate feeding, [15] and flux-assisted feeding [19] have been investigated to achieve particle entry into the melt. However, the majority of these nanoparticle feeding mechanisms have not been found to be promising in terms of incorporation of nanoparticles into the melt, mainly due to the formation of oxide on the liquid aluminum surface and oxide formation on aluminum foil in the case of the double capsulate feeding.…”