Ultrasound cavitation induced nucleation in metal solidification: An analytical model and validation by real-time experiments

Microstructural refinement of metallic alloys via ultrasonic melt processing (USMP) is an environmentally friendly and promising method. However, so far there has been no report in open literature on how to predict the solidified microstructures and grain size based on the ultrasound processing parameters.In this paper, an analytical model is developed to calculate the cavitation enhanced undercooling and the USMP refined solidification microstructure and grain size for Al-Cu alloys. Ultrafast synchrotron X-ray imaging and tomography techniques were used to collect the real-time experimental data for validating the model and the calculated results. The comparison between modeling and experiments reveal that there exists an effective ultrasound input power intensity for maximizing the grain refinement effects for the Al-Cu alloys, which is in the range of 20-45 MW/m(2). In addition, a monotonous increase in temperature during USMP has negative effect on producing new nuclei, deteriorating the benefit of microstructure refinement due to the application of ultrasound.

Automated summary

The microstructural refinement of metallic alloys using ultrasonic melt processing is an environmentally friendly and promising method. The study develops an analytical model to predict solidified microstructures and grain sizes for Al-Cu alloys based on ultrasound processing parameters. Results show that there is an optimal ultrasound power intensity range of 20-45 MW/m² for maximizing grain refinement effects for the alloys, and that a monotonous increase in temperature during ultrasonic processing has a negative impact on producing new nuclei and the microstructure refinement benefits.