Numerical modelling and experimental validation of the effect of ultrasonic melt treatment in a direct-chill cast AA6008 alloy billet

In-situ observations and acoustic measurements upon fragmentation of free-floating intermetallics under ultrasonic cavitation in water

“…In a real liquid metal system subjected to UST, it is essential that the entire melt volume undergoes treatment. Therefore, identifying the borders of the effective treatment domain becomes very important to ensure the effectiveness of ultrasonic treatment on crystal fragmentation, in order to optimise the processing of large melt volumes by using a single energy source (single sonotrode) [42] , [48] . In this section, we outline the spatial treatment domain in terms of the time required to fracture a single fixed crystal and relating it to the acoustic pressure field generated by the ultrasound.…”

Effects of Pulsed Magnetic Field Melt Treatment on Grain Refinement of Al-Si-Mg-Cu-Ni Alloy Direct-Chill Casting Billet

“…Many researchers have demonstrated that applying external fields is an effective method to improve the metallurgical quality of DC casting billets [15][16][17]. With the advantages of contactless, pollution-free, low-cost and easy operation, the application of electromagnetic fields, such as low-frequency electromagnetic fields and AC and DC combined magnetic fields, in the aluminum alloy DC casting process has become a research hotspot [18][19][20].…”

An overview and critical assessment of the mechanisms of microstructural refinement during ultrasonic solidification of metals

“…Abramov [16] , [17] and G. I. Eskin [10] , [18] to the fundamentals of UST and the commercial importance of applying UST to direct chill (DC) cast ingots and degassing processes in Al alloys are notable. Several research works published later on include lab-scale experiments that investigated (but are not limited to) the role of solute [19] , [20] , [21] and nucleant particles on grain refinement [22] , [23] , refinement of primary intermetallic phases [20] , [21] , [24] , solidification of immiscible systems [25] , degasification [26] , development of metal matrix nano-composites [27] , simulating the effect of temperature gradient and fluid flow affecting the solidification structure [28] , [29] , [30] , [31] . Transparent analogues [32] , [33] , [34] , [35] and water models [36] , [37] were used to understand the cavitation phenomenon, which progressed significantly with further advancement in in-situ characterization using X-ray synchrotron imaging techniques [38] , [39] , [40] , [41] , [42] .…”

“…The final section of this paper critically compares the refinement and the mechanism that promotes grain refinement in lab-scale conditions vs the direct chill (DC) casting process that employs UST in large-scale castings [30] , [31] , [67] . The importance of cold zones in the casting and how the onset of solidification near the relatively cold zones can produce finer grains when separated by vibration or agitations will also be discussed [54] , [55] , [68] .…”