作者: Jung Pyung Choi, Ki Bae Kim, Eui Pak Yoon
摘要: In general, the element (Sr, Na, Sb, etc.) is used as a modifier of eutectic Si phase in the hypoeutectic Al-Si system. When these elements are added into the hypoeutectic Al-Si melt, the flake shaped Si phase transforms to fibrous shape and the size of Si phase is also decreased. In this study, the electromagnetic vibration is adopted for modifying eutectic Si phase and reducing its size. The higher the current density and frequency of electromagnetic vibration(EMV), the finer the size of eutectic Si phase. The tensile strength and elongation of EMVed alloy were highly improved. Measured twin probability of EMVed alloy at a frequency of 1000Hz was approximately six times as high as that of the normal alloy and a half of that of Sr modified alloy. The mechanism for the increase in twin density due to EMV during solidification could be supposed from the fact that the preferential growth along <112> in silicon was suppressed by preventing Si atom from attaching to the growing interface of Si phase and by changing the solid/liquid interfacial energy of silicon.
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作者: Sung Chul Lim, Heung Bok Lee, Kyung Hoon Kim, Hyouk Chon Kwon
摘要: Most of the work reported at this conference concerned the semi-solid processing of low
melting point alloys, and in particular light alloys of aluminum and magnesium. Mg alloys are very
attractive as structural materials, because they are the lightest metal among all structural metal
materials and excellent specific strength. The purpose of this paper is to develop a semi-solid
microstructure of Mg alloys using electromagnetic stirring applicable for lighter automobile. The size
of primary solid particle and the degree of sphericity as a function of the variation in cooling rate,
stirring speed, and holding time were observed. By applying electromagnetic stirring, primary solid
particles became finer and rounder relative to as-cast sample. As the input Hz increased from 10Hz to
14Hz, particle size decreased. The size of primary solid particle was found to be decreased with
increasing cooling rate. Also, it decreased with stirring up to 3 minutes but increased above that point.
The degree of sphericity became closer to be 1 with hold time. Semi-solid microstructure of Mg
alloys, one of the low melting point alloys, could be controlled by electromagnetic stirring.
546
作者: Hai Tao Zhang, Hiromi Nagaum, Yu Bo Zuo, Jian Zhong Cui
摘要: A comprehensive mathematical model has been developed to describe the interaction of
the multiple physics fields during the conventional DC casting and LFEC (low frequency
electromagnetic casting) process. The model is based on a combination of the commercial finite
element package ANSYS and the commercial finite volume package FLUENT, with the former for
the calculation of the electromagnetic field and the latter for the calculation of the magnetic driven
fluid flow, heat transfer and solidification. Moreover, the model has been verified against the
temperature measurements obtained from two 7XXX aluminum alloy billets of 200mm diameter,
cast during the conventional DC casting and the LFEC casting processes. In addition, a
measurement of the sump shape of the billets were carried out by using addition melting metal of
Al-30%Cu alloy into the billets during casting process. There was a good agreement between the
calculated results and the measured results. Further, comparison of the calculated results during the
LFEC process with that during the conventional DC casting process indicated that velocity patterns,
temperature profiles and the sump depth are strongly modified by the application of a low
frequency electromagnetic field during the DC casting.
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作者: Zhi Hao Zhao, Jian Zhong Cui, Qing Feng Zhu
摘要: The horizontal direct chill (HDC) casting process is a well-established production route for
an aluminum alloy ingot; however, the ingot may suffer from inhomogeneous microstructures and
serious macrosegregation due to the unbalanced cooling condition and gravitational effect. In order to
control the defect, a low frequency electromagnetic field has been applied in the HDC casting process
and its influences on microstructures and macrosegregation have been studied. The results show that
the low frequency electromagnetic field can improve macrostructures, reduce inhomogeneous
microstructures and macrosegregation in HDC product; and two main parameters of the
electromagnetic field—density and frequency influence the microstructures and solution distribution
along the diameter of the ingot significantly. In the range of ampere-turns and frequency employed in
the experiments, the optimum ampere-turns and frequency have been found to be 10000At, 30Hz.
691
作者: Xiang Jie Wang, Jian Zhong Cui, Hai Tao Zhang, Qing Feng Zhu
摘要: During the low frequency electromagnetic casting process, the electromagnetic parameter plays an important role among the casting parameters. In this work, effects of electromagnetic parameters on the electromagnetic field and body force are analyzed by constructing a two-dimensional finite element model and using ANSYS software which is a kind of commercial FEM analysis software. The results show that the current frequency mainly influences the distribution of electromagnetic body force, the current intensity determines the intensity of electromagnetic body force, and the current frequency and intensity should be matched during the low frequency electromagnetic casting process.
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