Gangqiang WANG
,
Xiangyun TANG and Jusheng MA(Dept. of Materials Science and Engineering
,
Tsinghua University Beijing 100084
,
China)
材料科学技术（英）
Interfacial geometric morphology, chemistry and microstructure have been studied by SEM,EDAX, HREM, and XPS. It is found that the oxide scale/metal interface consists of two layers.The first one is amorphous SiO2 growing inward metal matrix, and the second one under the firstlayer is TiO2 distributing in metal matrix. There is microstructural transition zone at Cr2O3/SiO2intedece, and an atomic mixed zone with 8 nm width at Si02/metal interface. The transitionzone which is saturated with Cr diffusing from oxide scale exists at the oxide scale/glass intedece.The reasons why sand-blasting process can improve bonding strength of the oxide scale and themetal are also discussed. The ideal interfaces are proposed finally.
关键词:
Baicheng LIU
,
Wei QIU
,
Houfa SHEN
,
Zhiqiang GAO (Dept. of Mechanical Engineering
,
Tsinghua University Beijing 100084
,
China)
材料科学技术（英）
In this paper, an algorithm for simulating fluid flow and heat transfer for mold filling of shaped castings is presented. The main features of the algorithm include: 1) a simple but practical technique based on VOF method to determine free surface, 2) an explicit scheme of enthalpy to solve the energy equation more efficiently, and 3) an effective treatment to modify the flux deviation due to pressure iteration. In order to verify these methods, well controlled experiments have been repeatedly done with both water analog and gray iron pouring experiments to record the flow patterns and temperature variations. The calculated results are in accordance with the experimental ones. For the applications, the simulated initial temperature distribution right after mold filling was used to analyse subsequent solidification and to predict shrinkage defects.Actual castings were poured and tested in a foundry plant. The reuslts show that the defects predication with considering fluid flow effects is more precise than that without considering the effects.
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