Ultrasonic treatment: a clean technology that supports sustainability in casting processes

Simulation of Ultrasonic Induced Cavitation and Acoustic Streaming in Liquid and Solidifying Aluminum

“…With the distance-dependent decreasing pressure amplitude, cavitation gas volume fraction decreases as well during the transport of the cavitation bubbles from the active cavitation area through the acoustic streaming. In view of the influence of acoustic streaming on the solidification, a more homogeneous temperature distribution was recognizable, which together with cavitation finally influences the material's structure, as shown in [48]. Therefore, two streaming-related effects appear: (1) a more homogeneous solidification and structure as a result of continuous fluid mixing by acoustic streaming and (2) a faster solidification of the total cast, confirming the descriptions of [12,47].…”

“…The mold wall was defined as a boundary with heat transfer and a starting temperature of 673 K. Similar to the isothermal model, at the mesh boundaries, full reflection of sound waves/without any losses was calculated. According to the experimental setup in [48], the radiator had a frequency of 20 kHz, a peak-to-peak amplitude of 35 µm, a temperature of 473 K and was placed concentrically directly above the mold cavity. The same simulation was performed without UST to use the results as a reference.…”

“…This way, it could be possible to predict the beginning and development of cavitation and acoustic streaming, allow for overlap with simulations of the solidification process (as in [47]), or enable preinvestigations for process design. Furthermore, Lebon et al [41] noted rightly that the modeling behind the results in [48] was not further described. Therefore, a further goal is the more detailed description of the modeling and results behind this work.…”

Ultrasonic Cavitation Treatment of Metallic Alloys

“…It has been reported that the narrow size distribution of refiner particles after UST of Zr added to Mg [6] and Al-Ti-B [67], Al-Zr, Al-Zr-Ti [63] added to Al alloys results in better grain refinement. The refinement of blocky and needle shape primary intermetallic phases such as Al 3 Ti [63,68], Al 3 (Zr, Ti) [63,69], primary Si [70][71][72] and β/δ-Al-Fe-Si [24,25] phases is an added advantage of UST that further improves the mechanical properties of the cast alloys. Figure 7 shows a summary of the common intermetallic phases encountered in commercial Al alloys and their refinement after UST.…”

“…Similarly, it is found that the addition of Mn combined with UST in Al 17 Si 2 Fe(0.5 to 2.0)Mn alloys favoured the transformation to the desirable α-Al 15 (Fe,Mn) 3 Si 2 phase finely distributed with polygonal morphology [25]. The refinement of primary phase and its morphology is generally reported to be affected by both nucleation and fragmentation effects depending on the temperature range of UST applied during solidification [24,25,68].…”