Effects of high-intensity ultrasound on the microstructures and mechanical properties of ultra-large 2219 Al alloy ingot

The microstructural refinement of ultra-large 2219 Al alloy ingot is particularly important towards improving the corresponding mechanical properties for special industry application. Combined with the direct-chill casting, scalable high-intensity ultrasonic melt treatment (USMT) technique was applied to manufacture the ultra-large 2219 Al alloy cylindrical ingot (1380 mm in diameter and 4600 mm in length) in the present work. Then, the effects of USMT on the major microstructural constituents (i.e. primary alpha-Al grains, eutectic networks and precipitating particles) were investigated accordingly. The industry-level experiments showed that the major microstructural constituents were modified after introducing ultrasound. The primary alpha-Al phase was refined from the center part to the edge part compared with the ingot without USMT. The agglomeration of coarsening eutectic phase was mitigated and large lamellar eutectic networks became discontinuous from half radius to the edge part with USMT. Meanwhile, the mechanical properties of the solidified Al alloy ingots were also tested and compared between the samples with and without USMT. To reveal the modification of major microstructural constituents, the dominant mechanisms were proposed based on the ultrasonic cavitation and acoustic streaming.