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High-performance magnesium alloys are moving towards a trend of being produced on a large scale and in an integrated manner. The foundational key to their successful production is the high-quality cast ingots. Magnesium alloys produced through the conventional semi-continuous casting process inevitably contain casting defects, which makes it challenging to manufacture high-quality ingots. The integration of external field assisted controlled solidification technology, which combines physical fields such as electromagnetic and ultrasonic fields with traditional semi-continuous casting processes, enables the production of high-quality magnesium alloy ingots characterized by a homogeneous microstructure and absence of cracks. This article mainly summarizes the technical principles of those external field assisted casting process. The focus is on elaborating the refinement mechanism of different types of electromagnetic fields, ultrasonic fields, and combined physical fields during the solidification of magnesium alloys. Finally, the development prospects of producing highquality magnesium alloy ingots through semi-continuous casting under the external field were discussed. [ABSTRACT FROM AUTHOR]

A transient 3D model was established to investigate the effect of spatial interaction of ultrasounds on the dual-frequency ultrasonic field in magnesium alloy melt. The effects of insertion depth and tip shape of the ultrasonic rods, input pressures and their ratio on the acoustic field distribution were discussed in detail. Additionally, the spacing, angle, and insertion depth of two ultrasonic rods significantly affect the interaction between distinct ultrasounds. As a result, various acoustic pressure distributions and cavitation regions are obtained. The spherical rods mitigate the longitudinal and transversal attenuation of acoustic pressure and expand the cavitation volume by 53.7% and 31.7%, respectively, compared to the plate and conical rods. Increasing the input pressure will enlarge the cavitation region but has no effect on the acoustic pressure distribution pattern. The acoustic pressure ratio significantly affects the pressure distribution and the cavitation region, and the best cavitation effect is obtained at the ratio of 2:1 (P15:P20). [ABSTRACT FROM AUTHOR]