Scalable ultrasonic casting of large-scale 2219AA Al alloys: Experiment and simulation

Abstract

An ultra-large 2219 Al alloy ingot (i.e., 1.38 m in diameter and 4.6 m in length) was manufactured using a direct-chill casting technique assisted by four ultrasonic sonotrodes. Then, the effects of ultrasonication on the matrix grains, the α-Al/θ-Al2Cu eutectic structures and the macrosegregation of Cu were experimentally determined. Using numerical simulation, the distribution of physical fields (i.e., the liquid fraction, the temperature gradients and the velocity field) in the sump was simulated and compared between the ingots with and without ultrasonication. After introducing ultrasonication, grain refinement occurred due to the increased cooling rate generated by the accelerated heat transfer in the sump. Meanwhile, the macrosegregation of the major element (Cu) was relieved, which was mainly attributed to the effect of ultrasound-forced convection. Besides, eutectic growth was restricted in the narrowed mushy zone under ultrasound. As a result, eutectic agglomerations were accordingly reduced. The relevant mechanisms were discussed in terms of the experimental results and simulation.