采用超声驻波处理Al-20%Si合金熔体，研究不同超声驻波处理功率下Al-20%Si合金的微观组织演变，探讨超声驻波对 Al-20%Si 合金凝固过程的作用和组织细化的机理。结果表明：超声驻波能抑制初晶硅的析出，但声辐射力的作用使已析出的初晶硅偏聚长大；超声驻波处理能实现共晶硅“片状−纤维状”明显的形态转变，凝固后共晶硅转变为频繁分支细小的纤维状；超声功率越大，共晶硅“片状−纤维状”的形态转变越明显；超声驻波可以用于亚共晶Al-Si合金的变质处理中。%A hypereutectic Al-20%Si alloy was treated by ultrasonic standing wave and the microstructure evolution of Al-20%Si alloy was studied under different ultrasonic powers. The course of crystallization and mechanism of microstructural refinement for the ultrasonic treated alloy were also discussed. The results show that the precipitation of primary silicon is inhibited while the segregation and growth of primary silicon are promoted because of acoustic radiation force under the ultrasonic standing waves treatment. The morphology of eutectic Si is obviously changed after ultrasonic standing wave treatment, varying from flake to fiber shape. Eutectic Si is changed into fine fiber shape with many branches. With the increase of ultrasonic power, the morphological change of eutectic Si from flake to fiber shape is more obvious. Ultrasonic standing wave can be used in the modification of hypoeutectic Al-Si alloy.
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