Microstructure of Directionally Solidified Mg-Zn Alloy with Different Growth Rates

Abstract:

The influence of withdrawal rate on the microstructure of directionally solidified Mg-x%Zn (x=2, 4, 6) alloys was investigated in this paper. It was found that with the withdrawal rates increased from 20 μm/s to 60 μm/s, the morphology of the solid-liquid interface changed from planer to cellular dendrite. When the growth rate was further increased to 120 μm/s, the solidification microstructure appeared to be the typical dendrite structure with the developed secondary dendrite arms. Meanwhile, the dendrite arm spacing decreased with the increase of growth rate. Under the same solidification conditions, the microstructure went through cell branch transformation with the increase of Zn content within a lower withdrawal rate range; while the Zn content did not affect the morphology at a higher withdrawal rate. As well, the microstructure was refined gradually with the increase of Zn content. The effects of withdrawal rate and alloying content on morphology were analyzed by constitutional supercooling and the MS theory.

• Periodical: Materials Science Forum (Volume 816)
• Pages: 411-417
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.816.411
• Online since: April 2015
• Authors: Hong Min Jia, Xiaohui Feng, Yuan Sheng Yang*
• Keywords: Directional Solidification, Growth Rate, Mg-Zn Alloy, Microstructure Evolution

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