کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1795446 | 1023722 | 2008 | 6 صفحه PDF | دانلود رایگان |
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 200 μm/s, the microstructures consisted of leading α-Fe dendrites and peritectic Nd2Fe14B phase in the interdendritic region. At medium velocities of 425 and 500 μm/s, an incomplete banded structure formed, containing circles of α-Fe/Nd2Fe14B–Nd2Fe14B dendrites. At high velocities of 1, 3 and 5 mm/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 1–200 μm/s and high velocities of 3 and 5 mm/s. The incomplete dendritic bands at 425 and 500 μm/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 1 mm/s was interpreted by abundant nucleation and quick growth of Nd2Fe14B phase at the γ-Fe dendritic interface.
Journal: Journal of Crystal Growth - Volume 310, Issue 14, 1 July 2008, Pages 3366–3371