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| 1 | 偏晶溶液相分离过程的实时观测研究显示文摘为了揭示自由落体条件下偏晶合金壳核组织的形成机制,基于相似性原理设计了一种环形温度场,对丁二腈-52.6mol%H2O偏晶溶液的相分离过程进行了实时观测.发现在两个不混溶液相的分离过程中,富水相液滴经历了“析出→迁移→凝并→聚集”运动过程,最终形成以富水相为中心的两层壳核组织.同时测定了液滴的运动速率,并对Marangoni迁移速率进行了理论计算,两者能够较好地符合.由此证实了在偏晶溶液的相分离过程中,第二液相主要是在温度梯度的驱动下产生Marangoni迁移.这一实验直观地再现了落管无容器处理过程中液滴内部的相分离过程. | 翟薇 王楠 魏炳波 | 2007 | 物理学报2007，56，4： | 18 |
| 2 | 壳核组织形成过程的数值模拟研究显示文摘对空间环境条件下偏晶凝固过程中壳核组织的形成机制进行了数值模拟研究.在总自由能中引入表面自由能项对H模型进行了修正,使之能够描述表面偏析作用下的相分离.选取Fe-Cu合金作为模型体系,系统模拟了微重力状态下深过冷合金液滴的亚稳相分离过程,揭示了表面偏析效应和温度梯度引起的Marangoni对流对微观组织演化的影响.模拟结果表明,Fe65Cu35合金的相分离组织从弥散结构演化为3层壳核组织;Fe50Cu50合金经历了“双连续相→4层壳核→3层壳核”的组织演化;Fe35Cu65合金的组织由弥散结构向两层壳核组织演化.偏析作用使得最外层总是富Cu相,温度梯度引起的Marangoni对流决定了内部体相的组织演化过程. | 秦涛 王海鹏 魏炳波 | 2007 | 中国科学(G辑)2007，37，3： | 2 |
| 3 | Simulated evolution process of core-shell microstructures显示文摘The evolution process of core-shell microstructures formed in monotectic alloys under the space environment condition was investigated by the numerical simula- tion method. In order to account for the effect of surface segregation on phase separation, Model H was modified by introducing a surface free energy term into the total free energy of alloy droplet. Three Fe-Cu alloys were taken as simulated examples, which usually exhibit metastable phase separation in undercooled and microgravity states. It was revealed by the dynamic simulation process that the formation of core-shell microstructures depends mainly on surface segregation and Marangoni convection. The phase separation of Fe65Cu35 alloy starts from a dispersed structure and gradually evolves into a triple-layer core-shell micro- structure. Similarly, Fe50Cu50 alloy experiences a structural evolution process of 'bicontinuous phase → quadruple-layer core-shell → triple-layer core-shell', while the microstructures of Fe35Cu65 alloy transfer from the dispersed structure into the final double-layer core-shell morphology. The Cu-rich phase always forms the outer layer because of surface segregation, whereas the internal microstructural evolu- tion is controlled mainly by the Marangoni convection resulting from the tempera- ture gradient. | QIN Tao WANG HaiPeng WEI BingBo | 2007 | Science China(Physics,Mechanics & Astronomy)2007，50，4： | 0 |
| 4 | Heat and mass transfer characteristics during rapid solidification of Fe-Cu peritectic alloys显示文摘The viscose flow and microstructure formation of Fe-Cu peritectic alloy melts are investigated by analyzing the velocity and temperature fields during rapid solidifi-cation,which is verified by rapid quenching experiments.It is found that a large temperature gradient exists along the vertical direction of melt puddle,whereas there is no obvious temperature variation in the tangent direction of roller surface.After being sprayed from a nozzle,the alloy melt changes the magnitude and di-rection of its flow and velocity rapidly at a height of about 180 μm.The horizontal flow velocity increases rapidly,but the vertical flow velocity decreases sharply.A thermal boundary layer with 160-300 μm in height and a momentum boundary layer with 160-240 μm in thickness are formed at the bottom of melt puddle,and the Reynolds number Re is in the range of 870 to 1070 in the boundary layer.With the increase of Re number,the cooling rate increases linearly and the thickness of thermal boundary layer increases monotonically.The thickness of momentum boundary layer decreases slowly at first,then rises slightly and decreases sharply.If Re < 1024,the liquid flow has remarkable effects on the microstructure formation due to dominant momentum transfer.The separated liquid phase is likely to form a fiber-like microstructure.If Re>1024,the heat transfer becomes dominating and the liquid phase flow is suppressed,which results in the formation of fine and uniform equiaxed microstructures. | XU JinFeng DAI FuPing WEI BingBo | 2008 | Science China(Physics,Mechanics & Astronomy)2008，51，5： | 0 |
| 5 | 快速传热传质对Fe-Cu包晶合金凝固过程的作用机制显示文摘通过求解急冷熔体中的速度场和温度场,分析了快速凝固过程中Fe-Cu包晶合金熔体的黏性流动及其组织形成规律,并对理论结果进行了实验验证.发现合金熔体在急冷快速凝固过程中,沿液池的高度方向存在着较大的温度梯度,而在与辊面相切的水平方向上液池温度变化不甚显著.熔体自喷嘴喷出后,在高度约180μm处迅速改变流速的大小和方向:水平流速迅速增大,而高度方向的流速则急剧减小.液池底部存在高度为160~240μm的动量边界层和厚度为160~300μm的热边界层,边界层中的雷诺数Re在870~1070范围.随着Re数的增大,冷却速率呈线性增大,热边界层厚度单调增加,动量边界层厚度则呈现出非线性变化趋势.当Re〈1024时,动量传输作用较强,急冷液相的黏性流动比较显著,分离液相易于形成纤维状凝固组织;而当Re〉1024时,热量传输作用显著增强,液相流动受到抑制,容易获得均匀细小的等轴晶组织. | 徐锦锋 代富平 魏炳波 | 2007 | 中国科学(G辑)2007，37，4： | 0 |
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