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Energy paths of twin-related lattice reorientation in hexagonal metals via ab initio calculations

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Journal of Materials Science & Technology 2018年第4期34卷 700-707页

作者： Gang Zhou Lihua Ye Hao Wang Dongsheng Xu Changgong Meng Rui Yang Institute of Metal Research Chinese Academy of SciencesShenyang 110016China Dalian University of Technology Dalian 116024China

Employing ab initio calculations, we systematically investigated tile energy paths of [1012] twin-related lattice reorientation in hexagonal metals Be, Mg, Sc, Ti, Co, Y, Zr, Tc, Ru, Gd, Tb, Dy, Ho, Er, Tin, Lu, Hf, Re, and Os. Among the studied systems, lattice reorientation energy increases in the order of Mg, Gd, Tb, Dy, Zr, Tc, Ti, Ho, Y, Co, Er, Sc, Be, Tin, Lu, Hf, Re, Ru and Os. The reorientation process consists of shear and shuffle components. Concerning the significance of shuffle, these hexagonal metals fall into two groups. In the first group, which includes Mg, Co, Ru, Re and Os, regardless of the shear amount, subsequent shuffle is an energy-uphill process, while in the second group, which includes Ti, Tc, Be, Y. Gd, Tb, Dy, Ho, Zr, Er, Sc, Hf, Lu and Tin, shuffle becomes an energy-downhill process if shear component reaches an adequate level （at least 60%）. These results qualitatively explain the present observation of lattice reorientation in hexagonal metals, and shed light upon a general understanding on the [1012] twinning behavior in the aim of improving materials properties.

关键词： Hexagonal metal twin Shear Shuffle First-principles

High density stacking faults of ■ compression twin in magnesium alloys

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Journal of Materials Science & Technology 2019年第10期35卷 2263-2268页

作者： Bo Zhou Manling Sui Beijing Key Laboratory of Microstructure and Properties of Solids Institute of Microstructure and Properties of Advanced Materials Beijing University of Technology

■ compression twins with high density stacking faults were studied at atomic scale using Cscorrection transmission electron microscopy. On one side of the ■ twin boundary, there were many steps arranged alternately with the coherent twin boundaries. Most of the steps were linked with stacking faults inside twins. Burgers vector of twinning dislocations and the mismatch strain at steps were characterized. Due to the compressive mismatch strain at steps, the high density stacking faults inside twins were formed at twin tips during twinning process. The localized strain at the steps would be related to the crack nucleation in magnesium alloys.

关键词： Magnesium twin Stacking faults High resolution transmission electron microscopy

Construction and application of pre-classified smooth semi-supervised twin support vector machine

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Journal of Systems Engineering and Electronics 2019年第3期30卷 564-572页

作者： ZHANG Xiaodan QI Hongye School of Mathematics and Physics University of Science and Technology Beijing

In order to handle the semi-supervised problem quickly and efficiently in the twin support vector machine (TWSVM) field, a semi-supervised twin support vector machine (S2TSVM) is proposed by adding the original unlabeled samples. In S2TSVM, the addition of unlabeled samples can easily cause the classification hyper plane to deviate from the sample points. Then a centerdistance principle is proposed to pre-classify unlabeled samples, and a pre-classified S2TSVM (PS2TSVM) is proposed. Compared with S2TSVM, PS2TSVM not only improves the problem of the samples deviating from the classification hyper plane, but also improves the training speed. Then PS2TSVM is smoothed. After smoothing the model, the pre-classified smooth S2TSVM (PS3TSVM) is obtained, and its convergence is deduced. Finally, nine datasets are selected in the UCI machine learning database for comparison with other types of semi-supervised models. The experimental results show that the proposed PS3TSVM model has better classification results.

关键词： semi-supervised twin support vector machine (TWSVM) pre-classified center-distance smooth

The interaction and migration of deformation twin in an eutectic high-entropy alloy AlCoCrFeNi2.1

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Journal of Materials Science & Technology 2019年第5期35卷 902-906页

作者： Yaoli Zhang Jinguo Li Xinguang Wang Yiping Lu Yizhou Zhou Xiaofeng Sun Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Materials Science and Engineering University of Science and Technology of China Hefei 230026 China Key Laboratory of Space Manufacturing Technology Chinese Academy of Sciences Beijing 100094 China School of Materials Science and Engineering Dalian University of Technology Dalian 116024 China

An eutectic high-entropy alloy consisting Al, Co, Cr, Fe and Ni elements was prepared by vacuum directional solidification technology. The alloy exhibits excellent comprehensive mechanical performance during tension at temperature range of 600–700℃. The microstructure reveals the intersection of twintwin is the prevailing deformation mechanism and the twins play a dual role in strengthening and toughening the alloy in the thermomechanical process. The deformation twin variants I and were formed by the edge dislocation 112 and the mixed dislocation 211 on the {111} crystal planes, respectively. Besides, the dislocation jogs and kinks caused by twin intersection on the slip planes can strengthen the alloy, which may contribute to the high strength(the tensile strengths at the 600°and 700°tensile tests are respectively780 MPa and 630 MPa.). Moreover, the coherent twin boundary migration has the function of coordinating deformation and contributes to the high ductility of the alloy.

关键词： Eutectic high-entropy alloy Tensile properties Deformation twin Dislocation jog twin migration

End-point dynamic control of basic oxygen furnace steelmaking based on improved unconstrained twin support vector regression

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Journal of Iron and Steel Research International 2020年第1期27卷 42-54页

作者： Chuang Gao Ming-gang Shen Xiao-ping Liu Nan-nan Zhao Mao-xiang Chu School of Materials and Metallurgy University of Science and Technology LiaoningAnshan 114051LiaoningChina School of Electronic and Information Engineering University of Science and Technology LiaoningAnshan 114051LiaoningChina School of Information and Electrical Engineering Shandong Jianzhu UniversityJinan 250101ShandongChina

In order to improve the end-point hit rate of basic oxygen furnace steelmaking,a novel dynamic control model was proposed based on an improved twin support vector regression *** controlled objects were the end-point carbon content and *** proposed control model was established by using the low carbon steel samples collected from a steel plant,which consists of two prediction models,a preprocess model,two regulation units,a controller and a basic oxygen *** test results of 100 heats show that the prediction models can achieve a double hit rate of 90%within the error bound of 0.005 wt.%C and 15℃.The preprocess model was used to predict an initial end-blow oxygen ***,the double hit rate of the carbon con tent and temperature only achieves 65%.Then,the oxygen volume and coolant additi ons were adjusted by the regulation units to improve the hit ***,the double hit rate after the regulation is reached up to 90%.The results indicate that the proposed dynamic control model is efficient to guide the real production for low carbon steel,and the modeling method is also suitable for the applications of other steel grades.

关键词： Steelmaking Basic oxygen furnace End-point control twin support vector regression Wavelet transform

Two Dimension Finite Element Simulations on the Electromagnetic Containment in twin-Roll Strip Casting

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Journal of Materials Science & Technology 2003年第1期19卷 9-12页

作者： Peiwei BAO, Hongshuang DI, Xiaoming ZHANG, Guodong WANG and Xianghua LIUState Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110004, China Lab. of Rolling and Automat. Northeastern Univ. Shenyang 110004 China

Distribution of magnetic field and electromagnetic force in twin-roll casting of steels was studied by the method of numericalsimulation in this paper. Two-dimension finite element model, which includes the regions of melt, stainless collar, coil andmagnetic core, has been constructed. By solving magnetic vector potential formulations of quasi-static electromagnetic field,distribution of magnetic flux density and magnetic force at different molten height is determined. Calculated results showedthat intensity of the distribution of magnetic flux density increased linearly with the increased coil current; and the magneticforce in the melt increased as a quadratic cure with creased coil current. More attention was given to the distribution of eddycurrent and magnetic force in the melt, the confine effect at different molten height was also discussed.

关键词： twin roll casting Electromagnetic field Electromagnetic containment Simulation Finite element

twin structure of the lath martensite in low carbon steel

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Progress in Natural Science:Materials International 2016年第2期26卷 169-172页

作者： Pan Zhang Yulin Chen Wenlong Xiao Dehai Ping Xinqing Zhao School of Materials Science and Engineering Beihang University School of Materials Science and Engineering Dalian Jiaotong University

It has been well accepted that the martensites in quenched carbon steels exhibit two typical morphologies which are closely dependent on the carbon content, i.e. lath martensite in low carbon steels and lenticular martensite in high carbon steels. Based on conventional belief, the lath martensites in low carbon steels are with high density dislocations as the substructure, in contrast to twin substructure in lenticular high carbon martensite. In the present work, an intensive transmission electron microscopy investigation was made to characterize the microstructures of the lath martensite in a low carbon steel of 0.2 wt%C. It was found that lots of lath martensites consist of twin as their substructure, rather than high density dislocations. In addition, nanoscale precipitates cohering with ferrite matrix were found at the twin interfaces. The orientation relationships between the precipitates and the ferrite matrix are in good agreement with that of primitive hexagonal ω phase in titanium alloys and other bcc metals or alloys.

关键词： Martensite twin Lath Low carbon steel Martensitic transformation

Dynamic characteristics of charged droplets in an electrostatic spraying process with twin capillaries

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Chinese Journal of Chemical Engineering 2018年第12期26卷 2403-2411页

作者： Jun Zhang Hongzhou He Guanxing Huang Cleaning Combustion and Energy Utilization Research Center of Fujian Province School of Mechanical Engineering Jimei University Engineering training Centre Jimei University

The experimental and simulated investigations on electrostatic spraying with twin capillaries are carried out. The starting electric voltage required for the cone-jet and the deposition characteristics of the droplets are *** whole spraying process, which includes jet and droplet motions, is simulated and the simulated results on the motions of jet and droplet are basically consistent with the experiments. According to the simulated results,the contributions of various electric forces to droplet movement are quantitatively analyzed and the droplet dynamic characteristics, especially the interaction mechanism between two sprays, are revealed. The test results on the droplet deposition characteristics partially support the simulated results on the droplet motion. The present work is useful for a better understanding on the interaction between sprays in double or multi-capillary system.

关键词： Electrostatic spray twin capillaries Simulation Interaction

Structural characterization of the{1122}twin boundary and the corresponding stress accommodation mechanisms in pure titanium

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Journal of Materials Science & Technology 2021年第13期72卷 114-121页

作者： Bingqiang Wei Song Ni Yong Liu Min Song State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China

{11-22}compression twin plays an important role in accommodating deformation along the c axis of HCP ***,the studies on the interface structure of{11-22}twin boundary(TB),especially the twin tip,and the corresponding local stress release mechanism are still *** work studied the interface characters of{11-22}TB of a deformed pure titanium by transmission electron ***{11-22}TB presented serrated character,consisting of coherent twin boundary(CTB)and(0002)_(T)//(11-2-2)_(M)or(11-2-2)_(T)//(0002)_(M)steps,and the twin tip was fully composed of the basal-pyramidal(BPy)and pyramidal-basal(PyB)*** twin tip presents asymmetric morphology and the step height at the twin tip is much larger than that away from the twin *** types of local stress accommodation mechanisms were observed:zonal dislocation emission and hexagonal close packed structure to facecentered cubic structure *** zonal dislocation was produced by the dissociation of the1/3dislocation that was nucleated at the twin tip and the phase transformation was introduced by emission of Shockley partial dislocations from the{11-22}twin boundary.

关键词： {1122} twin twin boundary twinning dislocation Stress accommodation Titanium