骆良顺张宇民苏彦庆王新郭景杰傅恒志
金属学报
doi:10.3724/SP.J.1037.2010.00485
利用电阻加热和感应加热Bridgman定向凝固系统对非小平面包晶系模型合金Fe-Ni合金进行系统的定向凝固实验研究, 探索2种常规定向凝固条件下对流对包晶合金定向凝固过程中带状组织和宏观偏析的影响规律.发现在高G/V定向凝固过程中, 对流使包晶合金定向凝固过程中轴向和径向形成严重的宏观偏析, 从而使组织演化异常复杂且难以达到稳态.轴向宏观偏析体现在有限长试样从定向凝固开始至凝固结束都将发生初生相向包晶相的转变过程, 转变过程受合金成分和对流强度影响.径向宏观偏析体现在试样心部贫溶质易形成初生相, 边缘富集溶质易形成包晶相, 在径向上也存在初生相向包晶相的转变过程.
关键词:
包晶合金
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directional solidification
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convection
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segregation
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banding structure
刘俊诚
,
介万奇
,
周尧和
金属学报
利用水模拟实验，研究了ＡＣＲＴ（坩埚加速旋转技术）过程中Ｅｋｍａｎ流场的稳定性，及其与坩埚内径Φ，转速最大差值△ωｍａｘ，及坩埚中液体高度Ｈ的关系。结果表明，当雷诺数Ｒｅ＝０．６７８Ｒ（｜△ωｍａｘ｜／ｖ）０．５≤ＲｅＣｌ（下临界值）时，Ｅｋｍａｎ流场稳定；Ｒｅ≥ＲｅＣ２（上临界值）时，减速过程的Ｅｋｍａｎ流场完全不稳定。当Ｒｅ≤ＲｅＣｌ时，Ｅｋｍａｎ流区的高度ｈ随Φ及△ωｍａｘ增加而增加，Ｅｋｍａｎ流区相对高度ｈ／Ｒ（Ｒ＝０．５Φ）与Ｒｅ２呈线性关系，直线的斜率ｋ与Ｒ有关；当坩埚中液柱高度Ｈ减小到某一临界值Ｈ时，Ｅｋｍａｎ流区随Ｈ的减小而减小。
关键词:
坩埚加速旋转技术
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convection
,
crystal growth
Y.F. Zhu
,
W.Q. Zhang
,
Y.S. Yang
,
Q.M. Liu and Z.Q. Hu (State Key Lab. of RSA
,
Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang 110015
,
Chilla)
金属学报(英文版)
Macrosegregations and microstructures of Al-7%Si alloy solidified under complex of fects of magnetic field and centrifugal forces are studied by means of a set of selfdesigned electromagnetic centrifugal casting (EMCC) device. It is shown that electromagnetic field (EMF) has an important effect on the macrosegregation of centrifugal casting specimen of Al-7%Si alloy in two respects: one is that there exists always a kind of convection in the liquid in front of the S/L interface caused by effect ofthe electromagnetic force; the other is that different atomic clusters of solidparticles with different physical characteristics are subjected to quite different electromagnetic (Lorentz) force. Therefore, their movements get changed. In addition, the formation process of a complex band structure consisting of primary α-Al dendrites and (α-Al+β-Si) eutectics in hypoeutectic Al-Si alloys during EMCC and the effect of EMF are discussed.
关键词:
electromagnetic field (EMF)
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null
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null
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null
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null
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