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Microstructure quantification of Cu-4.7Sn alloys prepared by two-phase zone continuous casting and a BP artificial neural network model for microstructure prediction

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Rare Metals 2019年第12期38卷 1124-1130页

作者： Ji-Hui Luo xue-feng liu Zhang-Zhi Shi Yi-Fei liu School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China Beijing Laboratory of Metallic Materials and Processing for Modem Transportation University of Science and Technology BeijingBeijing 100083China

Microstructures of Cu-4.7Sn(%) alloys prepared by two-phase zone continuous casting(TZCC)technology contain large columnar grains and small grains.A compound grain structure,composed of a large columnar grain and at least one small grain within it,is observed and called as grain-covered grains(GCGs).Distribution of small grains,their numbers and sizes as well as numbers and sizes of columnar grains were characterized quantitatively by metallographic *** propagation(BP) artificial neural network was employed to build a model to predict microstructures produced by different processing *** of the model are five processing parameters,which are temperatures of melt,mold and cooling water,speed of TZCC,and cooling *** of the model are nine microstructure quantities,which are numbers of small grains within columnar grains,at the boundaries of the columnar grains,or at the surface of the alloy,the maximum and the minimum numbers of small grains within a columnar grain,numbers of columnar grains with or without small grains,and sizes of small grains and columnar *** model yields precise prediction,which lays foundation for controlling microstructures of alloys prepared by TZCC.

关键词： Two-phase zone continuous casting Cu-Sn alloy Grains-covered grains Microstructure quantification Back propagation artificial neural network

Rectifying control of wire diameter during dieless drawing by a deformation measuring method of interframe displacement

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International Journal of Minerals,Metallurgy and Materials 2012年第7期19卷 615-621页

作者： Yong He xue-feng liu Fang Qin Jian-xin Xie Key Laboratory for Advanced Materials Processing (Ministry of Education) University of Science and Technology Beijing Beijing 100083 China

A deformation measurement method of interframe displacement was proposed in this paper. By online monitoring the shape di- mensions of both the deformation zone and its adjacent zone by machine vision, the initial and terminative positions of deformation were dynamically identified during dieless drawing, and the global monitoring and online closed-loop control of the deformation zone were achieved. The dieless drawing process was systematically carried out on NiTi shape memory alloy wires. It is shown that the deformation measurement method of interframe displacement can track the axial displacement of the wires, but this cannot be achieved by traditional machine vision. The initial and terminative positions of deformation can be accurately identified by this method. The proposed rectifying control technology can effectively decrease the wire diameter fluctuation during dieless drawing, that is, the standard deviation of the wire diameter fluctuation could be decreased fi＇om 0.30 to 0.08 mm after three passes of dieless drawing, indicating that the control system has a good rectifying ability.

关键词： wire drawing rectification deformation machine vision closed loop control systems nickel alloys sha^oe memory effect

A fractal-based model for the microstructure evolution of silicon bronze wires fabricated by dieless drawing

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International Journal of Minerals,Metallurgy and Materials 2010年第6期17卷 770-776页

作者： Zhen Wang xue-feng liu Yong He Jian-xin Xie Key Laboratory of the Ministry of Education of China for Advanced Processing Technology of Materials University of Science and Technology Beijing Beijing100083 China State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

The back-propagation neural （BPN） network was proposed to model the relationship between the parameters of the dieless draw- ing process and the microstrecmres of the QSi3-1 silicon bronze alloy. Combined with image processing techniques, grain sizes and grain-boundary morphologies were respectively determined by the quantitative metallographic method and the flactal theory. The outcomes obtained show that the deformed microstructures exhibit typical fractal features, and the boundaries can be characterized quantitatively by ffactal dimensions. With the temperature of 600-800℃ and the drawing speed of 0.67-1.00 mm-s-1, either a lower temperature or a higher speed will cause a smaller grain size together with an elevated fractal dimension. The developed model can be capable for forecasting the microstructure evolution with a minimum error. The average relative errors between the predicted results and the experimental values of grain size and fractal dimension are 3.9% and 0.9%, respectively.

关键词： silicon bronze dieless drawing microstructure fractal dimension neural networks

High-strength aluminum alloys hollow billet prepared by two-phase zone continuous casting

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China Foundry 2022年第3期19卷 253-262页

作者： Yao-hua Yang xue-feng liu Wang-zhang Chen Beijing Advanced Innovation Center for Materials Genome Engineering University of Science and Technology BeijingBeijing 100083China Beijing Laboratory of Metallic Materials and Processing for Modern Transportation University of Science and Technology BeijingBeijing 100083China Key Laboratory for Advanced Materials Processing of Ministry of Education University of Science and Technology BeijingBeijing 100083China Shunde Graduate School University of Science and Technology BeijingFoshan 528399GuangdongChina

The two-phase zone continuous casting(TZCC)technique was used to continuously cast high-strength aluminum alloy hollow billets,and a verified 3D model of TZCC was used to simulate the flow and temperature fields at casting speeds of 2-6 mm·min^(-1).Hollow billets under the same conditions were prepared,and their macro/microstructures were analyzed by an optical microscope and a scanning electron *** the TZCC process,a circular fluid flow appears in front of the mushy zone,and the induction heated stepped mold and convective heat transfer result in a curved solidification front with depressed region near the inner wall and a vertical temperature *** deflection of the solidification front decreases and the average cooling rate in the mushy zone increases with increasing casting *** results for a 2D12 alloy show that hot tearing periodically appears in the hollow billet accompanied by macrosegregation near the inner wall at casting speeds of 2 and 4 mm·min^(-1),while macroscopic defects of hot tearing and macrosegregation weaken and the average size of columnar crystals in the hollow billets decreases with further increasing casting speed.2D12 aluminum alloy hollow billets with no macroscopic defects,the finest columnar crystals,and excellent mechanical properties were prepared by TZCC at a casting speed of 6 mm·min^(-1),which is beneficial for the further plastic forming process.

关键词： two-phase zone continuous casting high-strength aluminum alloy hollow billet fluid flow heat transfer columnar crystals

Processing limit maps for the stable deformation of dieless drawing

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International Journal of Minerals,Metallurgy and Materials 2011年第3期18卷 330-337页

作者： Yong He xue-feng liu Jian-xin Xie Hong-gang Zhang Key Laboratory for Advanced Materials Processing （MOE） University of Science and Technology Beijing Beijing 100083 China State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

Tin bronze wires were produced by dieless drawing. The effects of heating power, the distance between cooler and heater as well as feeding speed on the diameter, the temperature field, and the deformation region profile of the wires were investigated. The results indi-cated that each processing parameter exhibited both lower and upper limits of stable deformation based on the criterion of stable deformation with the diameter fluctuation of ±0.05 mm. Both the temperature and its gradient of the deformation region increased with increasing heating power under stable deformation, but decreased with an increase in feeding speed. As the distance between cooler and heater increased, the temperature of the deformation region increased and the slope of the deformation region profile decreased. The processing limit map of sta-ble deformation exhibited a closed curve and the unstable deformation consisted of wire breakage and diameter fluctuations.

关键词： tin bronze wire dieless drawing processing parameters turning method

Fabrication and characterization of novel biodegradable Zn-Mn-Cu alloys

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Journal of Materials Science & Technology 2018年第6期34卷 1008-1015页

作者： Zhang-Zhi Shi Jing Yu xue-feng liu Lu-Ning Wang School of Materials Science and Engineering University of Science and Technology Beijing

Zn-Mn-Cu alloys with micro-alloying of Mn and Cu in Zn are developed as potential biodegradable met- als. Although the as-cast alloys are very brittle, their ductilities are significantly improved through hot rolling. Among the as-cast and the as-hot-rolled alloys, as-hot-rolled Zn-0.35Mn-0.41 Cu alloy has the best comprehensive property. It has yield strength of 198.4 ± 6.7 MPa, tensile strength of 292.4 ± 3.4 MPa, elongation of 29.6 ±3.8% and corrosion rate of 0.050-0.062 mm a^-1. A new ternary phase is characterized and determined to be MnCuZn18, which is embedded in MnZn13, resulting in a coarse cellular/dendritic MnZna3-MnCuZn18 compound structure in Zn-0.75 Mn-0.40Cu alloy. Such a coarse compound structure is detrimental for wrought alloy properties, which guides future design of Zn-Mn-Cu based alloys. The preliminary research indicates that Zn-Mn-Cu alloy system is a promising candidate for potential cardiovascular stent applications.

关键词： Zn alloys Biodegradability Strength Ductility Corrosion behavior

Copper foils with gradient structure in thickness direction and different roughnesses on two surfaces fabricated by double rolling

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International Journal of Minerals,Metallurgy and Materials 2013年第12期20卷 1170-1175页

作者： Xi-yong Wang xue-feng liu Wen-jiang Zou Jian-xin Xie School of Materials Science and Engineering University of Science and Technology Beijing Beijing Laboratory of Metallic Materials and Processing for Modern Transportation University of Science and Technology Beijing Key Laboratory for Advanced Materials Processing Ministry of Education) University of Science and Technology Beijing

Copper foils with gradient structure in thickness direction and different roughnesses on two surfaces were fabricated by double rolling. The two surface morphologies of double-rolled copper foils are quite different, and the surface roughness values are 61 and 1095 nm, respectively. The roughness value of matt surface can meet the requirement for bonding the resin matrix with copper foils used for flexible printed circuit boards, thus may omit traditional roughening treatment; the microstructure of double-rolled copper foils demonstrates an obviously asymmetric gradient feature. From bright surface to matt surface in thickness direction, the average grain size first increases from 2.3 to 7.4 μm and then decreases to 3.6 μm; compared with conventional rolled copper foils, the double-rolled copper foils exhibit a remarkably increased bending fatigue life, and the increased range is about 16.2%.

关键词： copper foils rolling surfaces gradient structure fatigue of materials

Single-atom catalysis for advanced oxidation and reduction systems in water decontamination

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Rare Metals 2024年第8期43卷 3576-3606页

作者： Jie Teng Jin-Hui Xu Wen-Xin Sun xue-feng liu Xia Xu Guo-Shuai liu School of Urban Construction Changzhou UniversityChangzhou 213164China School of Environmental and Civil Engineering Jiangnan UniversityWuxi 214122China

Water scarcity is an escalating global crisis,posing a severe threat to populations ***,exploring various materials to remove emerging contaminants from freshwater sources has garnered significant *** this regard,single-atom catalysis(SACs) has emerged as a catalyst of scientific progress in water purification and treatment methodologies during recent *** exhibit exceptional catalytic activity,selectivity and stability,due to their near-perfect atom utilization,highly unsaturated coordination environment and uniform reaction ***,a comprehensive and critical review encompassing the successful integration of SACs into water purification processes needs to be *** review aims to accentuate recent trends by presenting the synthesis,structure,and environment and energy application-relevant properties of *** results show that a comprehensive and multi-perspective summary of the advantages of SACs in environmental remediation can have significant benefits,such as fast kinetics,costeffectiveness,*** oxidation and reduction processes of SACs and functional SACs materials in water purification were ***,the last section is devoted to the current research gaps and further perspectives on the application of SACs in water treatment,which are summarized and analyzed.

关键词： Single-atom catalysis Water treatment Oxidation Reduction

Crystallography of precipitates in Mg alloys

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Journal of Magnesium and Alloys 2021年第2期9卷 416-431页

作者： Zhang-Zhi Shi Hong-Ting Chen Ke Zhang Fu-Zhi Dai xue-feng liu Beijing Laboratory of Metallic Materials and Processing for Modern Transportation Key Laboratory for Advanced Materials Processing of Ministry of EducationSchool of Materials Science and EngineeringUniversity of Science and Technology BeijingBeijing 100083China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China

Crystallography of precipitates in Mg alloys is indispensable to explain and predict alloy microstructures and *** order to obtain a global understanding of diversified experimental results,a general theory of singular interface is introduced,which provides the physical base and calculation methodology for interpreting precipitate morphology and orientation relationship(OR),especially useful for understanding irrational facets and *** by the theory,recent experimental findings are systematically summarized,including thermally stable and metastable precipitates with various crystal ***,theoretical advances inspired by the findings are introduced,which deepens our understanding on OR selection and preference of irrational *** last,future research directions in this field are proposed.

关键词： Mg alloys Precipitation Facet Orientation relationship