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Transactions of Nonferrous Metals Society of China 2018年第1期28卷 9-19页

作者： Guang-yuan YAN Feng MAO Zhi-qiang CAO Ting-ju LI Tong-min WANG School of Materials Science and Engineering Dalian University of Technology Dalian 116024 China Key Laboratory of Solidification Control and Digital Preparation Technology (Liaoning Province) Dalian 116024 China

Three-layer6009/7050/6009aluminum alloy clad slab was fabricated by an innovative direct-chill casting *** study the response of the clad slab to plastic deformation and heat treatments,homogenization annealing,hot rolling,solution and aging were successively performed on the as-cast6009/7050/6009clad *** results revealed that excellent metallurgical bonding between7050alloy layer and6009alloy layer was achieved under optimal *** clad ratio obviously decreased when the annealed sample was rolled to55%hot reduction level,and then changed slightly with further ***,the content of rodlike Zn-rich phases increased significantly in7050alloy layer in the homogenized clad samples after rolling at55%,65%and75%hot reduction levels,and the higher level of hot reduction resulted in narrower diffusion *** solution and aging significantly improved the hardness in7050alloy layer,interfaces and6009alloy layers of the rolled samples except for the thin side for the75%hot reduction sample.

关键词： aluminum alloy three-layer clad slab direct-chill casting plastic deformation heat treatment

Numerical simulation for macrosegregation in direct-chill casting of 2024 aluminum alloy with an extended continuum mixture model

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Transactions of Nonferrous Metals Society of China 2018年第5期28卷 1007-1015页

作者： Hai-jun LUO Wan-qi JIE Zhi-ming GAO Yong-jian ZHENG State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi＇an 710072 China Chair of Simulation and Modeling of Metallurgical Processes Montan Universitaet Leoben 8700 Leoben Austria

An extended continuum mixture model for macrosegregation is applied to predicting Cu and Mg segregation in large-size ingot of 2024 aluminum alloy during direct chill casting（DC）. A microsegregation model using the approximate phase diagram data was coupled with macroscopic transport equations for macrosegregation profiles. Then, the impacts of transport mechanisms on the formation of macrosegregation were discussed. It is found that copper and magnesium have a similar segregation configuration from the billet center to surface. Negative segregation is observed in the centerline and subsurface, whereas positive segregation is obtained in the surface and somewhat underestimated positive segregation in the middle radius. Further, the discrepancy between the predicted and experimental results was discussed in detail. The results show that the magnesium to some extent alleviates the copper segregation in ternary alloy, compared with that in binary alloy. The predicted results show good agreement with measured experimental data obtained from literatures.

关键词： direct-chill casting macrosegregation numerical simulation continuum model 2024 aluminum alloy

Characteristics evolution of 6009/7050 bimetal slab prepared by direct-chill casting process

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Transactions of Nonferrous Metals Society of China 2016年第4期26卷 895-904页

作者：闫光远毛丰陈飞吴伟曹志强王同敏李廷举大连理工大学材料科学与工程学院三束材料改性教育部重点实验室大连116024 大连理工大学原材料特种制备技术实验室大连116024

6009/7050 alloy bimetal slab was prepared by a direct-chill (DC) casting process. Homogenizing annealing, hot rolling and T6 treatment were successively performed and their effects on microstructure and properties of the slab were studied. The results reveal that the average diffusion layer thickness of as-cast slab, determined by interdiffusion of elements Zn, Cu, Mg and Si, was about 400 μm. Excellent metallurgical bonding was achieved because all tensile samples fractured on the softer 6009 alloy side after homogenizing annealing. After homogenizing annealing plus rolling, the average diffusion layer thickness decreased to 100 μm, while the network structure of 7050 alloy side transformed to dispersive nubby structure. Furthermore, subsequent T6 treatment resulted in diffusion layer thickness up to 200 μm and an obvious increase of the Vickers hardness for both 7050 and 6009 sides. The layered structure of the as-cast 6009/7050 bimetal is retained after hot rolling and T6 treatment.

关键词： 7050 alloy bimetal slab direct-chill casting heat treatment hot rolling

Thermal-stress Simulation of direct-chill casting of AZ31 Magnesium Alloy Billets

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Journal of Wuhan University of Technology(Materials Science) 2009年第3期24卷 376-382页

作者：胡红军 College of Materials Science and Engineering Chongqing University National Engineering Research Center for Magnesium Alloys Chongqing University College of Material Science and Engineering Chongqing University of Technology

Two-dimensional （2D） transient coupled finite element model was developed to compute the temperature and stress field in cast billets, so as to predict the defects of the I-type billets made from AZ31 magnesium alloy and find the causes and solutions for surface cracks and shrinkages during direct-chill （DC） casting process. Method of equivalent specific heat was used in the heat conduction equation. The boundary and initial conditions used for primary and secondary cooling were elucidated on the basis of the heat transfer during the solidification of the billet. The temperature and the thermal-stress fields were simulated with the thermal-structural coupled module of ANSYS software. The influences of casting parameters on the distributions of temperature and stress were studied, which helped optimize the parameters （at pouring temperature of 680 ℃, casting speed of 2 min/s, heat-transfer coefficient of the second cooling equals to 5 000 W/m^2.℃^-1）. The simulation results of thermal stress and strain fields reveal the formation mechanism of some casting defects, which is favourable for optimizing the casting parameters and obtain high quality billets. Some measures of controlling processes were taken to prevent the defects for direct-chill casting billets.

关键词： magnesium alloy direct-chill casting temperature and stress fields numerical simulation solidification model

Macro-physical field of large diameter magnesium alloy billet electromagnetic direct-chill casting:A comparative study

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Journal of Magnesium and Alloys 2020年第3期8卷 716-730页

作者： Yonghui Jia Xingrui Chen Qichi Le Hang Wang Lei Bao Key Laboratory of Electromagnetic Processing of Materials Ministry of EducationNortheastern University314 MailboxShenyang 110819People's Republic of China

A comprehensive two-dimensional axisymmetric mathematical model that couples transient electromagnetic force with fluid flow,heat transfer,and solidification was established to describe the interaction of multiphysics field during DC *** melt flow,heat transfer,and solidification characteristics under differential phase pulse magnetic field and differential phase low-frequency electromagnetic field(DP-PMF and DP-LFEF)were numerically investigated by means of numerical simulation during electromagnetic direct-chill(DC)casting of AZ31 alloy at the same casting *** effects of differential phase electromagnetic fields on Lorentz forces distributions,melt flow,heat transfer,and liquid sump shape were discussed *** on measured current waveform,the results were compared with those obtained without magnetic field(MF)and under conventional pulse magnetic field(PMF)and low-frequency electromagnetic field(LFEF)under the same *** results show that the application of magnetic fields can significantly change the solidification process of DC *** phase magnetic fields(DP-LFEF and DP-PMF)can effectively reduce the temperature of the melt in the liquid sump,and the shallower liquid sump depth can be obtained under the differential phase magnetic fields.A large velocity vibration amplitude and a lower temperature are available simultaneously under DP-PMF,resulting in more uniform temperature distribution.

关键词： Magnesium alloy Differential phase magnetic field Low-frequency magnetic field Heat transfer direct-chill casting Numerical simulation

Microstructure and mechanical properties of NZ30K alloy by semi-continuous direct chill and sand mould casting processes

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China Foundry 2011年第1期8卷 41-46页

作者： Zheng Xingwei Dong Jie Liu Wencai Ding Wenjiang National Engineering Research Centre of Light Alloy Net Forming Shanghai Jiao Tong University Key State Laboratory of Metal Matrix Composite Shanghai Jiao Tong University Shanghai 200240 China

The Mg-3.0Nd-0.2Zn-0.4Zr (NZ30K) alloys were prepared by direct-chill casting (DCC) and sand mould casting (SMC) processes,respectively and their microstructures and mechanical properties were *** results indicate that casting method plays a remarkable influence on the microstructure and mechanical properties of as-cast NZ30K *** grain size increases from 35-40μm in the billets made by the DCC to about 100-120μm in the billets by the *** aggregation of Mg12Nd usually found at the triple joints of grain boundaries in the billets prepared by SMC while is not observable from the billets by *** tensile strengths and elongations of the billets are 195.2 MPa and 15.5% by DCC,and 162.5 MPa and 3.2% by SMC,*** tensile strength of the alloy by DCC is remarkably enhanced by T6 heat treatment,which reached 308.5 *** surfaces of NZ30K alloy have been characterized as intergranular fracture by SMC and quasi-cleavage fracture by DCC,respectively.

关键词： NZ30K alloy direct-chill casting microstructure mechanical properties

Effect of casting speed on floating grains and macrosegregation ofdirect-chill cast 2024 alloy with intensive melt shearing

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Transactions of Nonferrous Metals Society of China 2021年第3期31卷 565-575页

作者： Xu-dong LIU Qing-feng ZHU Zhi-meng LI Cheng ZHU Rui WANG Tao JIA Zhi-hao ZHAO Jian-zhong CUI Yu-bo ZUO Key Lab of Electromagnetic Processing of Materials Ministry of EducationNortheastern UniversityShenyang 110004China College of Materials Science and Engineering Northeastern UniversityShenyang 110004China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110004China

The ingot was prepared by direct-chill(DC)casting technology with different casting speeds under the influence of intensive melt shearing to explore the effect of casting speed and intensive melt shearing on the floating grains and negative centerline *** results indicate that the application of intensive melt shearing in DC casting process can distribute the floating grains uniformly,reduce the area fraction of the floating grains,alleviate the negative centerline segregation,and improve the uniformity of temperature field in the *** is also suggested that under the influence of intensive melt shearing,the casting speed plays a crucial role in the amounts and distribution of floating *** low casting speed,the intensive melt shearing can significantly reduce the area fraction of the floating grains and distribute them uniformly throughout the ***,this effect gradually disappears with the increase of casting speed.

关键词： direct-chill casting intensive melt shearing macrosegregation floating grains casting speed 2024 aluminum alloy

Nonmechanical criteria proposed for prediction of hot tearing sensitivity in 2024 aluminum alloy

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Transactions of Nonferrous Metals Society of China 2018年第5期28卷 848-857页

作者： M.H.GHONCHEH S.G.SHABESTARI A.ASGARI M.KARIMZADEH School of Metallurgy and Materials Engineering Iran University of Science and Technology Center of Excellence for High Strength Alloys Technology School of Metallurgy and Materials EngineeringIran University of Science and Technology School of Mechanical Engineering Iran University of Science and Technology

Two theoretical criteria represented by Katgerman, and Clyne and Davies for prognosticating hot tearing sensitivity were compared. Both unrefined and grain-refined samples of Al2024 alloy were solidified at various cooling rates ranging from 0.4 to 17.5 °C/s. Thermal analysis was used to detect dendrite coherency point and temperature of eutectic reaction. Curves of solid and liquid fractions were plotted based on Newtonian method to determine hot tearing susceptible areas. The experimental results show that the most susceptible zone in which hot tearing can occur in Al2024 is where Al_2CuMg intermetallic compound forms as a eutectic phase at last stage of mushy-state interval. Also, both criteria are in a good agreement with each other at high cooling rates used in direct-chill casting process while Clyne and Davies＇ model is more acceptable to determine hot tearing tendency from low to medium cooling rates.

关键词： 2024 aluminum alloy dendrite coherency direct-chill casting thermal analysis hot tearing

Prediction of grain structure in direct-chill cast Al–Zn–Mg–Cu billets using cellular automaton-finite element method

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Progress in Natural Science:Materials International 2021年第3期31卷 434-441页

作者： Min-Seok Kim Sang-Hwa Lee Jae-Gil Jung Kwangjun Eah Department of Materials Science and Engineering Gachon University Metallic Materials Division Korea Institute of Materials Science Department of Materials Science and Engineering Yonsei University

A cellular automaton-finite element(CA-FE) model was used to predict the solidification grain structure of permanent mold cast A7086 alloy. In this model, a Gaussian distribution of nucleation sites was adopted, and the Kurz-Giovanola-Trivedi model was extended to a multicomponent Al–Zn–Mg–Cu alloy system to determine the growth kinetics of the dendrite tip. For describing the Gaussian distribution of nucleation sites on the mold surface, an empirical relationship between the initial cooling rate of the melt and the nucleation density was proposed. Under various casting conditions, the calculated grain structures agreed well with the experimental results. Subsequently, the model was applied to the direct-chill(DC) cast billets, and the simulated grain structures reproduced well the experimental results. This confirmed that the current CA-FE model can be used practically and effectively in DC casting processes.

关键词： Cellular automaton-finite element (CA-FE) model direct-chill casting Al–Zn–Mg–Cu alloy A7068 alloy Grain structure