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Progress in Natural Science:Materials International 2019年第1期29卷 81-87页

作者： Yajun Luo Zhifeng Zhang Department of Mechanical Engineering Hunan Institute of Engineering General Research Institute for Non-Ferrous Metals Hunan Provincial Key Laboratory of Vehicle Power and Transmission System Hunan Institute of Engineering

Uniform direct chill(UDC) casting method was developed by combining annular electromagnetic stirring(AEMS) with intercooling in direct chill casting. In order to investigate effect of UDC on flow patterns, temperature profiles and solidification during the casting, a numerical model of the UDC casting process was developed and used to simulate the UDC casting process for preparing 7005 aluminum alloy billets. The comparison of the calculated results of UDC casting with normal direct chill(NDC) casting indicated that flow patterns, temperature profiles and the sump depth are modified remarkably by the application of annular electromagnetic stirring and intercooling during the direct chill casting. The sump profile and the temperature history during UDC casing were studied, and the mechanism of the casting process were discussed. The comparisons between the simulations and experimental results suggested that the proposed model provides good agreement for the sump profiles and the temperature history within the billets.

关键词： Aluminum alloy direct chill casting Simulation Electromagnetic stirring Intercooling

Structures and macrosegregation of a 2024 aluminum alloy fabricated by direct chill casting with double cooling field

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China Foundry 2022年第1期19卷 1-8页

作者： Cheng Zhu Zhi-hao Zhao Qing-feng Zhu Gao-song Wang Yu-bo Zuo Gao-wu Qin Research Center for Metallic Wires School of Materials Science and EngineeringNortheastern UniversityShenyang 110819China Key Laboratory of Electromagnetic Processing of Materials Ministry of EducationNortheastern UniversityShenyang 110819China Key Laboratory of Anisotropy and Texture of Materials Ministry of EducationNortheastern UniversityShenyang 110819China

Central region coarse grains and centerline segregation are common defects in aluminum ingots fabricated by direct chill(DC)casting.A double cooling field was introduced into the DC casting process to reduce these defects,whereby the external cooling was supplied by the mold and water jets,and intercooling was achieved by inserting a rod of the same alloy into the molten pool along the central axis of the *** than forming a good metallurgical interface during solid-liquid compound casting,in the present work,the purpose of inserting the rod is to enforce internal cooling and consequently decrease the sump ***,the insertion provides more nucleation sites with the unmoltenα-Al *** structure and the macrosegregation of 2024 Al alloy ingots prepared by DC casting with and without the inserts were *** show that when the inserting position is 50 mm above the upper edge of the graphite ring,significant grain refinement in the central region of the ingot and a reduced centerline segregation are achieved.

关键词： aluminum alloy direct chill casting double cooling field grain refinement macrosegregation

Effect of harmonic magnetic field and pulse magnetic field on microstructure of high purity Cu during electromagnetic direct chill casting

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China Foundry 2021年第2期18卷 141-146页

作者： Lei Bao Da-zhi Zhao Yin-ji Zhao Yong-hui Jia Xuan Wang Qi-chi Le Key Lab of Electromagnetic Processing of Materials Ministry of EducationNortheastern UniversityShenyang 110819China School of Materials Science and Engineering Northeastern UniversityShenyang 110819China

The effects of two types of magnetic fields,namely harmonic magnetic field(HMF)and pulse magnetic field(PMF)on magnetic flux density,Lorentz force,temperature field,and microstructure of high purity Cu were studied by numerical simulation and experiment during electromagnetic direct chill *** magnetic field is induced by a magnetic generation system including an electromagnetic control system and a cylindrical crystallizer of 300 mm in diameter equipped with excitation coils.A comprehensive mathematical model for high purity Cu electromagnetic casting was established in finite element *** distributions of magnetic flux density and Lorentz force generated by the two magnetic fields were acquired by simulation and experimental *** microstructure of billets produced by HMF and PMF casting was *** show that the magnetic flux density and penetrability of PMF are significantly higher than those of HMF,due to its faster variation in transient current and higher peak value of magnetic flux *** addition,PMF drives a stronger Lorentz force and deeper penetration depth than HMF does,because HMF creates higher eddy current and reverse electromagnetic field which weakens the original electromagnetic *** microstructure of a billet by HMF is composed of columnar structure regions and central fine grain *** contrast,the billet by PMF has a uniform microstructure which is characterized by ultra-refined and uniform grains because PMF drives a strong dual convection,which increases the uniformity of the temperature field,enhances the impact of the liquid flow on the edge of the liquid pool and reduces the curvature radius of liquid ***,PMF shows a good prospect for industrialization.

关键词： high purity Cu pulse magnetic field harmonic magnetic field microstructure sputtering target direct chill casting

Microstructure and mechanical properties of Mg-Nd-Zn-Zr billet prepared by direct chill casting

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Journal of Magnesium and Alloys 2018年第1期6卷 95-99页

作者： Xingwei Zheng Jie Dong Shiming Wang College of Engineering Science and Technology Shanghai Ocean University201306 ShanghaiPR China National Engineering Research Center of Light Alloy Net Forming Shanghai Jiao Tong University200240 ShanghaiPR China

High-quality Mg-Nd-Zn-Zr magnesium alloy billets with diameter of 200 mm were successfully prepared by direct chill(DC)*** results show that microstructures of the as-cast billet prepared by DC casting are mainly composed of equiaxed a-Mg and Mg 12 Nd eutectic compound distributing along the grain *** average grain size decreases along the radius of the *** the alloying elements of Nd and Zn distribute homogeneously across the large *** optimum process parameters for DC casting of the Mg-Nd-Zn-Zr magnesium alloy billet with diameter of 200 mm have been experimentally determined as follows:casting temperature 710℃ and casting speed 80 mm/min.

关键词： Magnesium alloy direct chill casting Microstructure Mechanical properties

Prediction of hot tearing susceptibility of direct chill casting of AA6111 alloys via finite element simulations

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Transactions of Nonferrous Metals Society of China 2020年第12期30卷 3161-3172页

作者： Dong-xu CHEN Rui-feng DOU Jia-qiang HAN Jun-sheng WANG School of Materials Beijing Institute of TechnologyBeijing 100081China School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China Advanced Research Institute of Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China

To predict hot tearing susceptibility(HTS)during solidification and improve the quality of Al alloy castings,constitutive equations for AA6111 alloys were developed using a direct finite element(FE)method.A hot tearing model was established for direct chill(DC)casting of industrial AA6111 alloys via coupling FE model and hot tearing *** applying this model to real manufacture processes,the effects of casting speed,bottom cooling,secondary cooling,and geometric variations on the HTS were *** results show that the HTS of the billet increases as the speed and billet radius increase,while it reduces as the interfacial heat transfer coefficient at the bottom or secondary water-cooling rate *** model shows the capabilities of incorporating maximum pore fraction in simulating hot tearing initiation,which will have a significant impact on optimizing casting conditions and chemistry for minimizing HTS and thus controlling the casting quality.

关键词： vehicle light-weighting AA6111 alloy direct chill casting hot tearing criterion pore fraction finite element simulation

Efects of low frequency electromagnetic ield on surface quality, microstructure and hot-tearing tendency of semi-continuous casting ZK60 magnesium alloy billets

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China Foundry 2013年第6期10卷 351-354页

作者： Zhang Zhiqiang Le Qichi Bao Lei Cui Jianzhong Key Laboratory of Electromagnetic Processing of Materials Ministry of Education Northeastern University

The low frequency electromagnetic field was applied during direct chill(DC) semi-continuous casting of the ZK60 magnesium alloy billets. Effects of low frequency electromagnetic field on surface quality, microstructure and hot-tearing tendency of Φ500 mm ZK60 magnesium alloy billets were investigated. The results showed that with the application of the low frequency electromagnetic field, the surface quality of the ZK60 magnesium alloy billets is markedly improved and the depth of cold fold is decreased. The microstructure of the billets is also significantly refined. Besides, the distribution of the grain size is relatively uniform from the billet surface towards its center, where the average grain size is 42 μm at surface and 50 μm at center. It also shows that the hot-tearing tendency of DC semi-continuous casting ZK60 magnesium alloy billets is significantly reduced under low frequency electromagnetic field.

关键词： ZK60 magnesium alloy billets direct chill casting low frequency electromagnetic field refinement

Effect of withdrawal rate on microstructure of a hypoeutectic Al-Si alloy by low superheat DC casting

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China Foundry 2013年第3期10卷 172-175页

作者： Zhao Dazhi Liu Fang Yu Fuxiao Hong Tao Zuo Liang Department of Metal Forming School of Materials and Metallurgy Northeastern University Key Lab. for Anisotropy and Texture of Materials (Ministry of Education) Northeastern University Xinjiang Joinworld Co. Ltd.

To obtain the billet with homogeneous and spheroidized primary grains is the key step in the semi- solid forming process. Among the semi-solid billet preparation methods, the process of low-superheat direct chill （DC） casting is simpler and more effective. In this study, the billets of AISi7Mg alloy were prepared by low- superheat DC casting at various withdrawal rates. The effect of withdrawal rate on the surface quality of the billets was investigated, and the evolution mechanism of the microstructural morphology in the billets was analyzed. The results show that the periodic corrugations and a large quantity of fine shrinkage pits appear in the billet surface when the withdrawal rate is 100 ***-1, and the above defects in the billet surface can be eliminated completely when the withdrawal rate is above 150 ***-1. But when the withdrawal rate is too fast （250 ***-1）, the primary a grains, except the ones in the billet center, have not enough time for ripening due to the high silidification rate, and will solidify as the dendrite structure. When the withdrawal rate is between 150 - 200 ***-1, the dendritic growth of the primary a grains is effectively inhibited, and a billet of AISi7Mg alloy with a smooth surface and homogeneous, fine, non-dendritic grains can be obtained.

关键词： direct chill casting AlSi7Mg alloy withdrawal rate