EFFECTS OF Al–Al4C3 REFINER AND ULTRASONIC FIELD ON MICROSTRUCTURES OF PURE Mg

Abstract

The melt of pure Mg was inoculated at the conditions of different addition amounts of Al-Al4C3 refiner. When adding 1.0%Al-Al4C3 refiner, the refining effect is the best and the average grain size of �-Mg is reduced from millimeter level to 106 µm. Ultrasound fields with different power levels were applied on the melt of pure magnesium and the best refining effect was obtained when the power was 600 W. The results show that the undercooling formed by breakdown of cavitation bubbles may have a promoting effect to nucleate. The breakdown of cavitation bubbles and the agitations of acoustic stream on the melt cause the fragmentation of fine dendritic crystal which could form new crystallization nuclei, this process plays the main role for nucleating in the melt. The combined application of ultrasound and Al-Al4C3 refiner to the melt of pure Mg could significantly refine its grain. The mechanism would be an the activation effect of ultrasound on the impurities in the melt. KEY WORDS ultrasound field, pure Mg, Al4C3, grain refinement