Ultrasonic refinement of magnesium by cavitation: Clarifying the role of wall crystals

Qian, Ma; Ramirez, A.; Das, A.

doi:10.1016/j.jcrysgro.2009.04.036

Cited by 131 publications

(53 citation statements)

References 18 publications

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“…In contrast, it was found that the wall crystal mechanism from a titanium sonotrode has a negligible effect on the grain refinement of a Mg-3Al-1Zn (wt.%) alloy under a range of experimental conditions [16] indicating that detachment may or may not occur depending on other casting conditions. For example, another factor that may affect ultrasonic grain refinement is the influence of the sonotrode material and this issue has not as yet received serious attention.…”

Section: Discussionmentioning

confidence: 89%

“…A number of hypotheses have been proposed on this basis. The major ones may be summarised as cavitation-enhanced heterogeneous nucleation, cavitation-induced dendrite fragmentation, and vibration-stimulated separation of wall crystals from the sonotrode surfaces [12,13,15,16]. Each of these mechanisms has been reviewed in Ref.…”

Section: Introductionmentioning

confidence: 99%

“…Each of these mechanisms has been reviewed in Ref. [16]. Ultrasonication can be introduced in a variety of approaches [12,16].…”

Section: Introductionmentioning

confidence: 99%

“…[16]. Ultrasonication can be introduced in a variety of approaches [12,16]. For a light metal or alloy melt UT is typically realized by inserting a sonotrode into the melt.…”

Section: Introductionmentioning

confidence: 99%

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The role of ultrasonic treatment in refining the as-cast grain structure during the solidification of an Al–2Cu alloy

Wang¹,

Dargusch²,

Qian³

et al. 2014

Journal of Crystal Growth

120

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Abstract. The effect of Ultrasonic Treatment (UT) over selected temperature ranges during cooling and solidification of an Al-2Cu alloy melt on the grain structure and cooling behaviour of the alloy has been investigated using a molybdenum sonotrode introduced without preheating. UT was applied over various temperature ranges before, during and after the nucleation of primary aluminium grains. It was found that ultrasonic grain refinement was achieved only when UT was applied from more than 20 o C above the liquidus temperature until below the liquidus temperature after nucleation has occurred. Applying UT from 40 o C or 60 o C above the liquidus to just above the liquidus brings the melt to a condition that favours nucleation, survival of the nucleated grains and their subsequent transport throughout the melt. Continuing to apply UT beyond the liquidus for a short time enhances both nucleation and convection thereby ensuring the formation of a fine, uniform equiaxed grain size throughout the casting. The lack of grain refinement when UT was applied from 20 o C above the liquidus temperature or from temperatures below the liquidus temperature is attributed to the formation of a strong solidified layer on the sonotrode which hinders the effective transmission of ultrasonic irradiation into the liquid metal. The application of a preheated sonotrode showed that formation of a solid layer can be prevented by preheating the sonotrode to 285 o C. Thus, an appropriate amount of superheat of the liquid metal or sufficient preheating of the sonotrode is necessary for ultrasonic grain refinement when a sonotrode is introduced into the melt.

show abstract

Section: Discussionmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

“…Each of these mechanisms has been reviewed in Ref. [16]. Ultrasonication can be introduced in a variety of approaches [12,16].…”

Section: Introductionmentioning

confidence: 99%

“…[16]. Ultrasonication can be introduced in a variety of approaches [12,16]. For a light metal or alloy melt UT is typically realized by inserting a sonotrode into the melt.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The role of ultrasonic treatment in refining the as-cast grain structure during the solidification of an Al–2Cu alloy

Wang¹,

Dargusch²,

Qian³

et al. 2014

Journal of Crystal Growth

120

View full text Add to dashboard Cite

show abstract

“…Up to now, two prevailing hypotheses have been proposed based on the cavitation phenomenon. One is cavitation-enhanced nucleation, due to nucleus activation and/or heightened supercooling [12], and the other is cavitation-induced dendrite fragmentation, arising from the shock wave generated by the collapse of cavitation bubbles [13].…”

Section: Discussionmentioning

confidence: 99%

Effect of Ultrasonic Treatment on the Solidification Microstructure of Die-Cast 35CrMo Steel

Liang

Chen

Zhou

et al. 2016

Metals

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Abstract:The effects of ultrasonic treatment (UST) on the solidification microstructure of a 35CrMo steel cast ingot were investigated. To avoid the erosion of a high-temperature melt, a T-shaped ultrasonic waveguide unit was used to introduce ultrasonic vibrations into a 35CrMo steel die casting melt. The experimental results show that the microstructure of the ingot was refined by ultrasonic treatment. While the microstructure of untreated 35CrMo steel is coarse dendritic grains, after the introduction of ultrasonic treatment, the solidification microstructure transforms from coarse dendritic to equiaxed grains, and the dendrites are also refined. Samples from different positions of the ingots were subjected to different ultrasonic effects, and the effects on grain refinement also varied due to the severe attenuation of the ultrasound in the melt. The mechanisms of grain refinement using ultrasonic treatment for 35CrMo steel melt are presented.

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Grain Refining of Pure Aluminum

Han¹,

Vian²,

Song³

et al. 2012

Light Metals 2012

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Ultrasonic refinement of magnesium by cavitation: Clarifying the role of wall crystals

Cited by 131 publications

References 18 publications

The role of ultrasonic treatment in refining the as-cast grain structure during the solidification of an Al–2Cu alloy

The role of ultrasonic treatment in refining the as-cast grain structure during the solidification of an Al–2Cu alloy

Effect of Ultrasonic Treatment on the Solidification Microstructure of Die-Cast 35CrMo Steel

Grain Refining of Pure Aluminum

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