Microstructure formation and phase selection in the solidification of Al_2O_3–5 at% SiO_2 melts by splat quenching
Microstructure formation and phase selection in the solidification of Al_2O_3–5 at% SiO_2 melts by splat quenching
复制标题
Al_2O_3–5 at% SiO_2 熔体溅射淬火凝固过程中的显微组织形成和相选择
DOI：
10.1557/jmr.2002.0300
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发表时间：
2002
影响因子：
2.7
通讯作者：
K. Kuribayashi
中科院分区：
文献类型：
--
作者：
Mingjun Li;K. Nagashio;K. Kuribayashi
在航空声悬浮装置中悬浮Al_2O_3- 5at%SiO_2试样，然后在连续波CO_2激光束加热系统的作用下熔化。当降低激光功率时，样品可以高度过冷。使用抛光良好的铜作为激冷砧，可以在规定的温度下通过溅射淬火实现快速凝固。当熔体在ΔT = 50 K淬火时，观察到非小面晶团向强小面晶枝晶的转变，表明动力学粗糙化对形貌转变的贡献可能是重要的。在微观组织观察的基础上，分析了冲击、铺展和凝固过程。当考虑动力学效应时，附加过冷度与距离呈指数关系。根据提出的附加过冷度讨论了形核行为，以说明不同区域形核布居数的差异。当熔体过冷度增加到190 K时，获得了多晶夹杂嵌入非晶基体的双相组织。连续冷却转变曲线被提出来解释淬火时的相选择。本文的观察结果和提出的获得高附加过冷度的模型对阐明他人的工作是有用的。
An Al_2O_3–5 at% SiO_2 specimen was levitated in an Aero-Acoustic Levitation apparatus and then melted when a continuous-wave CO_2 laser beam heating system was incorporated. The sample can be highly undercooled when decreasing the laser power. Rapid solidification by splat quenching can be realized at defined temperatures, using well-polished copper as chilling anvils. Microstructure transition from nonfaceted colony to strong faceted dendrites was observed when the melt was quenched at ΔT = 50 K, indicating that a kinetic contribution for roughening the microstructure may be significant for the morphology transition. The impacting, spreading, and solidifying processes were analyzed on the basis of microstructure observation. The additional undercooling was suggested to vary per an exponential relation with distance when the kinetic effect was taken into account. The nucleation behavior was also discussed according to the proposed additional undercoolings to demonstrate the difference in nucleation population at various regions. When the melt undercooling increases to 190 K, a double-phase structure with small polycrystalline inclusion embedded into amorphous matrix was obtained. The continuous cooling transformation profile was proposed to account for the phase selection upon quenching. The present observation and suggested model for acquiring high additional undercoolings are useful in elucidating the work of others.