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Your search keyword '"Lü, Haiyan"' showing total 4 results
Start Over Author "Lü, Haiyan" Topic directional solidification
4 results on '"Lü, Haiyan"'

3. Microstructure Selection Involving Nucleation in Directionally Solidified Nd-Fe-B Peritectic Alloys

Author

Liu Lin, Fu Hengzhi, Zhong Hong, Lü Haiyan, LI Shuangming, and Zou Guangrong

Subjects
Growth velocity, Equiaxed crystals, Materials science, Morphology (linguistics), Phase (matter), Metallurgy, General Engineering, Nucleation, Thermodynamics, Liquidus, Microstructure, Directional solidification
Abstract

Directional solidification experiments were performed on Nd 14 Fe 79 B 7 alloys to investigate microstructure formation related to nucleation. It was found that a small amount of α-Fe dendrites with equiaxed morphology existed in specimens grown at 200 and 500 μm/s. A banded structure showing alternate growth of α-Fe and Nd 2 Fe 14 B dendrites, was formed in the specimen at 500 μm/s. The formation of the equiaxed morphology microstructure or the banded structure is attributed to the phase nucleation ahead of the solidifying interface, since an undercooled zone corresponding to γ-Fe liquidus would appear ahead of the growing γ-Fe interface at the growth velocity of 200 and 500 μm/s. However, at growth velocity of 500 μm/s, only an undercooled zone corresponding to Nd 2 Fe 14 B liquidus would appear. These undercooled zones cause the nucleation of γ-Fe and Nd 2 Fe 14 B phases, resulting in the different microstructure patterns. The theoretical predictions are in good agreement with the experimental results.

Published
2009

4. Microstructure evolution of peritectic Nd14Fe79B7 alloy during directional solidification

Author

Zhong, Hong, Li, Shuangming, Lü, Haiyan, Liu, Lin, Zou, Guangrong, and Fu, Hengzhi

Subjects
*MICROSTRUCTURE, *ALLOYS, *DIRECTIONAL solidification, *MICROMECHANICS
Abstract

Abstract: Bridgman type directional solidification experiments were carried out in Nd14Fe79B7 alloy. Microstructure evolutions along with growth velocities were investigated. At low velocities from 1 to 200μm/s, the microstructures consisted of leading α-Fe dendrites and peritectic Nd2Fe14B phase in the interdendritic region. At medium velocities of 425 and 500μm/s, an incomplete banded structure formed, containing circles of α-Fe/Nd2Fe14B–Nd2Fe14B dendrites. At high velocities of 1, 3 and 5mm/s, a transition from γ-Fe dendrites to Nd2Fe14B dendrites occurred. Phase selection phenomena were theoretically studied using the extremum criterion which assumes growth-controlled phase selection. The theoretical results are in agreement with experimental results at low velocities of 1–200μm/s and high velocities of 3 and 5mm/s. The incomplete dendritic bands at 425 and 500μm/s were explained by nucleation of Nd2Fe14B phase at the γ-Fe dendritic interface, and growth competition between γ-Fe and the nucleated Nd2Fe14B phase. Phase transition from γ-Fe to Nd2Fe14B at 1mm/s was interpreted by abundant nucleation and quick growth of Nd2Fe14B phase at the γ-Fe dendritic interface. [Copyright &y& Elsevier]

Published
2008
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