【作者】 王海燕；

【导师】 王文魁； 刘日平； 孙力玲；

【作者基本信息】 燕山大学 ， 材料学， 2005， 博士

【摘要】 本文利用高压、落管、离子束溅射等技术,研究了远离平衡条件下 Fe-Si 合金的结构演化及β-FeSi₂相的形成。 研究了 Fe-66.7at.%Si 合金在高压和落管无容器条件下的凝固行为。与常压下凝固的典型共晶组织不同,高压条件下 Fe-66.7at.%Si 合金的凝固组织为初生ε相树枝晶加离异共晶。高压下凝固组织的变化主要是与压力对相图的影响和对凝固过程中溶质原子扩散的影响有关。通过引入压力参量,推导了高压凝固过程中的成分过冷判据,并应用该判据分析了高压凝固树枝晶组织的形成机理。研究了 Fe-66.7at.%Si合金液滴的无容器凝固过程中形核和生长方式随过冷度和冷却速率的变化规律。随样品直径减小,初生α相发生“小平面生长→非小平面生长”转变,ε+α共晶组织形态也发生了改变。在直径 0.2 mm 合金小球中,同一样品的不同位置凝固组织也发生了这种转变。这是由于不同的过冷度和冷却速率引起的。 采用闭管化学气相输运法制备得到β-FeSi₂单晶,并研究了温度场和载荷气体压强对晶体生长的影响。 采用离子束溅射铁靶的方法在加热的 Si（111）衬底上得到了不同种类的铁硅化物。当衬底温度为 973 K 时得到厚度为 500 nm 的单相、多晶和局部外延的β-FeSi₂薄膜。薄膜和 Si 衬底之间界面明显,没有中间层。采用离子束溅射法制备了 4 周期和 10 周期的[20 nm Fe/64 nm Si]多层膜,所得多层膜在 973 K 真空退火 60 mins 得到厚度分别为 360 nm 和 850 nm 的单相 β-FeSi2薄膜。 利用原位 X-射线衍射法进行了 Fe/Si 多层膜的结构和互扩散研究,确定出 Fe/Si多层膜在低温（573 K-623 K）退火过程中的互扩散系数为: D_L （T ）= 4.53×10_-22 exp（-0.16eV/K_BT） [m²/s]更多还原

【Abstract】 Under various conditions, such as high pressure, free falling, and ion beam sputtering, the structural evolution in Fe-Si binary alloy under far from equilibrium conditions and the β-FeSi₂ phase formation have been investigated. Solidification behaviors of the Fe-66.7at.%Si alloy under high pressure and during free falling were investigated. Different from the eutectic structure of the Fe-66.7at.%Si alloy solidified at ambient pressure, the microstructures of the alloy solidified at high pressures are composed of the dendritic primary phase and the anomalous eutectic. The significant changes in microstructure result from the change of phase diagram and the solute atom diffusion induced by high pressure. By introducing the pressure parameter, the correctional composition undercooling criterion was attained. Formation mechanism of the dendritic primary phase under high pressure was analyzed according to the correctional criterion. Containless solidification of the Fe-66.7at.%Si alloy was achieved in a 3 m drop tube. With decreasing droplet diameter, the growth mode of the primary phase α changes from faceted to nonfaceted growth and the eutectic changes from needle-like to anomalous eutectic. At the different sites of the droplet with the diameter of 0.2 mm, the same growth mode transition occurs. The different cooling rates and undercooling levels are responsible for the morphology changes. β-FeSi₂ single crystals were prepared by chemical vapor transport technique at substrate temperature 1023 K and source FeSi₂ temperature 1323 K. Influences of the temperature distribution and the carrier gas pressure on crystal growth were investigated. Different kinds of iron silicides were prepared at different Si（111） substrate temperatures by ion beam sputtering with an iron target. The β-FeSi₂ film with the thickness of 500 nm was obtained when the Si（111） substrate was heated to 973 K. The β-FeSi₂ film obtained was locally epitaxial and the interface between the film and the substrate was sharp. Monophase β-FeSi₂ films 360 nm and 850 nm in thickness were also successfully prepared by post-annealing 4-period and 10-period [20 nm Fe/64 nm Si] multilayers at 973 K for 60 minutes. The structural properties and interdiffusion of Fe/Si multilayers were investigated by in-situ X-ray diffraction method. Diffusivities at low temperature（573K-623K） can be described as: D_L （T ）= 4.53×10_-22 exp（-0.16eV/K_BT） [m²/s]更多还原