| Effect of cooling rates on the dendritic morphology transition of Mg–6Gd alloy by in situ X-ray radiography |
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| 摘 要： | The effect of cooling rate on the transition of dendrite morphology of a Mg-6 Gd(wt%) alloy was semiquantitatively analyzed under a constant temperature gradient by using synchrotron X-ray radiographic technique. Results show that equiaxed dendrites, including exotic 'butterfly-shaped' dendrite morphology, dominate at high cooling rate(1 K/s). When the cooling rate decreases in the range of 0.5–1 K/s, the equiaxed-to-columnar transition takes place, and solute segregates at the center of two long dendrite arms(LDA) of the 'butterfly-shaped' dendrite. When the cooling rate is lower than 0.3 K/s, directional solidification occurs and the columnar dendritic growth direction gradually rotates from the crystalline axis to the thermal gradient direction with an increase in cooling rate. Meanwhile, interface moves faster but the dendrite arm spacing decreases. Floating, collision and rotation of dendrites under convection were also studied in this work.
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| 收稿时间： | 4 March 2017 |
Effect of cooling rates on the dendritic morphology transition of Mg–6Gd alloy by in situ X-ray radiography |
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| Authors: | Yongbiao Wang Liming Peng Yanzhou Ji Xiaoxing Cheng Cunlong Wang Yujuan Wu Yanan Fu Long-Qing Chen |
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| Affiliation: | 1. National Engineering Research Center of Light Alloy Net Forming and State Key Laboratory of Metal Matrix Composite, Shanghai Jiao Tong University, Shanghai, 200240, China;2. Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, 16802, USA;3. Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Shanghai, 215600, China |
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| Abstract: | The effect of cooling rate on the transition of dendrite morphology of a Mg-6Gd (wt%) alloy was semiquantitatively analyzed under a constant temperature gradient by using synchrotron X-ray radiographic technique. Results show that equiaxed dendrites, including exotic ‘butterfly-shaped’ dendrite morphology, dominate at high cooling rate (>1?K/s). When the cooling rate decreases in the range of 0.5–1?K/s, the equiaxed-to-columnar transition takes place, and solute segregates at the center of two long dendrite arms (LDA) of the ‘butterfly-shaped’ dendrite. When the cooling rate is lower than 0.3?K/s, directional solidification occurs and the columnar dendritic growth direction gradually rotates from the crystalline axis to the thermal gradient direction with an increase in cooling rate. Meanwhile, interface moves faster but the dendrite arm spacing decreases. Floating, collision and rotation of dendrites under convection were also studied in this work. |
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| Keywords: | Synchrotron X-ray radiography Mg-Gd alloy Cooling rate 6-fold equiaxed dendrite ‘Butterfly-shaped’ Dendrite |
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