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The mathematical model of wetting angle of heterogeneous nucleation

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Science China(Technological Sciences) 2004年第4期47卷 391-397页

作者： HUANG Cheng1, SONG Bo1, MAO Jinghong2 & ZHAO Pei3 1. School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China 2. School of Material Science, University of Science and Technology Beijing, Beijing 100083, China 3. Central Iron and Steel Research Institute, Beijing 100081, China School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing China School of Material Science University of Science and Technology Beijing Beijing China Central Iron and Steel Research Institute Beijing China

The heterogeneous nucleation has been analyzed in terms of the thermodynamic theory, and the mathematical model of wetting angle of heterogeneous nucleation has been developed based on the dynamic requirements of hetero- and homogeneous nucleation. With the wetting angel model, the wetting angles of different catalysts in liquid iron have been calculated. The result shows that the wetting angle of most catalysts is smaller than 40, and the value of f() is far less than 1. The wetting angles of TiN, TiC and RE2O3 are smaller, while the wetting angle of MnO is bigger among the ordinary nucleation catalysts. The wetting angles calculated by this model are in agreement with the results of other research work.

关键词： heterogeneous nucleation, mathematical model, wetting angle, undercooling.

Morphologies of Fe-66.7 at.%Si alloy solidified in a drop tube

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Science China(Physics,Mechanics & Astronomy) 2005年第6期48卷 658-666页

作者： WANG Haiyan1,2, LIU Riping1, MA Mingzhen1, JING Qin1, LI Gong1, SUN Liling2 & WANG Wenkui1,2 1. Key Laboratory of Metastable Materials Science & Technology, Yanshan University, Qinhuangdao 066004, China 2. Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China Key Laboratory of Metastable Materials Science & Technology Yanshan University Qinhuangdao China Institute of Physics Chinese Academy of Sciences Beijing China

Solidification of 0.1―1.0 mm diameter droplets of Fe-66.7 at.%Si alloy was achieved in a 3 m drop tube. The XRD, EDS, and SEM measurements reveal that all the droplets are composed of the primary phase α and the α+ε eutectic. 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. In addition, the width of the primary phase α decreases with decreasing droplet size. The different cooling rates and undercooling.levels corresponding to the samples with different sizes are responsible for the morphology changes. The cooling rates of the samples with different diameters during free fall were calculated and their effects on the microstructure formation were discussed. This kind of transition is also found inside the same sample, which is due to the larger cooling rate on the surface than at the center.

关键词： Fe-Si alloy, solidification, drop tube, undercooling.

Rapid eutectic growth during free fall

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Chinese Science Bulletin 2002年第15期47卷 1316-1320页

作者： Wenjing Yao Xiujun Han Bingbo Wei Northwestern Polytech Univ Dept Appl Phys Lab Mat Sci Space Xian 710072 Peoples R China

Rapid eutectic growth of Sb-24%Cu alloy is realized in the drop tube during the free fall under the con-tainerless condition. Based on the analysis of crystal nuclea-tion and eutectic growth in the free fall condition, it is indicated that, with the increase of undercooling. microstruc-tural transition of Sb-24%Cu eutectic alloy proceeds from lamellar to anomalous eutectic structure. undercooling. of 0 -154 K have been obtained in experiment. The maximum undercooling.exceeds to 0.19TE. Calculated results exhibit that Cu2Sb compound is the primary nucleation phase, and that the primary Sb dendrite will grow more rapidly than the eutectic structure when undercooling.is larger than 40 K. The eutectic coupled zone around Sb-24%Cu eutectic alloy leads strongly to the Cu-rich side and covers a composition range from 23.0% to 32.7%Sb.

关键词： drop tube microgravity eutectic growth eutectic cou-pled zone high undercooling.

High undercooling.and rapid dendritic growth of Cu-Sb alloy in drop tube

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Chinese Science Bulletin 2002年第15期47卷 1312-1316页

作者： Yao Wenjing Xiujun Han Bingbo Wei Northwestern Polytech Univ Dept Appl Phys Lab Mat Sci Space Xian 710072 Peoples R China

Droplets of Cu-20%Sb hypoeutectic alloy has been rapidly solidified in drop tube within the containerless condition. With the decrease of droplet diameter, undercooling.increases and the microstructures of primary copper dendrite refines. undercooling.up to 207 K (0.17 TL) is obtained in experiment. Theoretic analysis indicated that, because of the broad temperature range of solidification, the rapid growth of primary copper dendrite is controlled by the solutal diffusion. Judging from the calculation of T0 curve in the phase diagram, it is shown that the critical undercooling.of segregationless solidification is △T0=474 K. At the maximum undercooling.of 207 K, the growth velocity of primary copper phase exceeds to 37 mm/s, and the distinct solute trapping occurs.

关键词： drop tube rapid solidification dendritic growth high undercooling.