Effect of different ultrasonic power on the microstructure and action mechanism of large-scale 2219 aluminum alloy ingots

Ultrasonic-assisted direct chill (USDC) casting can effectively mitigate the inherent drawbacks of conventional vertical direct chill (DC) casting. Herein, we investigate the microstructural evolution of large-sized (Φ830 mm) 2219 aluminum alloy ingots at varying ultrasonic power levels, and employ Fluent-based simulations to elucidate the underlying ultrasonic action mechanism in the melt. Results show that USDC-processed ingots feature significantly finer α-Al grains and a lower area fraction of coarse eutectic phases than those fabricated by conventional DC casting. Optimal performance is attained at an ultrasonic power of 500 W, achieving a maximum grain refinement efficiency of 65.47%, a 32.2% reduction in coarse eutectic area fraction, and a low Cu segregation degree of 0.061. Notably, both experimental and simulation results confirm that higher ultrasonic power does not necessarily translate to optimal melt processing effects. Accordingly, the relationship between ultrasonic output power and average grain size was fitted, which can offer valuable insights for industrial-scale production.