Comparison of Si Refinement Efficiency of Electromagnetic Stirring and Ultrasonic Treatment for a Hypereutectic Al-Si Alloy
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The effects of electromagnetic stirring, ultrasonic treatment (UT), and their combination on the Si particles refinement in a hypereutectic Al-Si alloy (A390) were examined. All three physical methods yielded a considerable change in the shape and size of the particles, with UT producing the finest size. The creation of holes inside the Si particles via the explosion of cavitation bubbles was determined to occur before fragmentation of primary Si. In addition, transmission electron microscopy analysis revealed twin formation on primary Si particles by application of an external field in the liquid. UT of the melt was sufficient to produce fine primary Si particles with average size of ~12 µm. The primary Si particles refinement and eutectic Si modification improved the mechanical properties.
Keywordsaluminum alloy automotive grain refinement microstructure solidification
The authors express their appreciation to the Conselho Nacional de Desenvolvimento Científico e Tecnológico CNPq process number 190088/2014-1 and the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP—Project: 2013-09961-3 and 2015-22143-3) for their financial support. The authors would also like to extend their appreciation to the School of Mechanical Engineering at the University of Campinas (UNICAMP).
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