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MAThEMATICAL MODELLING OF PhASE TRANSFORMATION FROM hOT-DEFORMED AUSTENITE IN LOW CARBON STEELS

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Acta Metallurgica Sinica(English Letters) 2003年第3期16卷 204-210页

作者： Y.B.xu G.D.Wang x.h.liu State Key Laboratory of Rolling And Automation Northeastern University Shenyang 110004 ChinaState Key Laboratory of Rolling And AutomationNortheastern University Shenyang 110004 ChinaState Key Laboratory of Rolling And AutomationNortheastern University Shenyang 110004 China

On the basis of superelement model, Cahn’s transformation kinetics theory and Scheil’s additivity rule, the CCT diagrams and transformation kinetics in low carbon steel were predicted considering both undeformed and deformed conditions. The influence of deformation on phase equilibria and transformation incubation period was evaluated quantitatively. The recrystallization kinetics and the evolution of dislocation density were calculated during continuous cooling. The results show deformation considerably shortens transformation incubation period, accelerates transformation kinetics and makes CCT curve shift leftwards. The calculated CCT diagrams and the volume fraction of each phase are in good agreement with measurements.

关键词： thermodynamics transformation kinetics continuous cooling hot-deformed austenite

MEChANICAL STABILIZATION OF DEFORMED AUSTENITEDURING CONTINUOUS COOLING TRANSFORMATION IN AC-Mn-Cr-Ni-Mo PLASTIC DIE STEEL

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Acta Metallurgica Sinica(English Letters) 1998年第2期11卷 93-99页

作者： D.S.liu G.D.Wang x.h.liu G.Z.Cui Northeastern Univ Shenyang China

The influence of prior austenite deformed at different temperature on the subsequent continuous cooling bainitic transformation has been investigated in an C-Ma-Cr-Ni-Mo plastic die steel. The results show that the prior deformation in low temperature region of austenite retards significantly the bainitic transformation. For the same continuous cooling schedule, as austenite deformed at lower temperature, the quantity of the classical sheaf-like bainite becomes less. The present results show that severe deformation leads to mechanical stabilization of austenite and causes the difficulty of bainitic ferrite propagation into the austenite.

关键词： plastic die steel deformed austenite continuous cooling bainitic transformation mechanical stabilization of austenite

hOT DUCTILITY OF 304hC STAINLESS STEEL AND ThE MODEL OF RESISTANCE TO DEFORMATION

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Acta Metallurgica Sinica(English Letters) 2003年第2期16卷 97-103页

作者： h.S.Di G.Z.Cui G.D.Wang x.h.liu State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110004ChinaState Key Laboratory of Rolling and AutomationNortheastern UniversityShenyang 110004ChinaState Key Laboratory of Rolling and AutomationNortheastern UniversityShenyang 110004ChinaState Key Laboratory of Rolling and AutomationNortheastern UniversityShenyang 110004China

The ductility map of 304hC stainless was determined by using the Gleeble-1500 dynamic thermal-mechanical simulator. The effect of Cu on the hot ductility of 304hC stainless steel was analyzed and the mathematical model of resistance to deformation was established. The microstructure, inclusion and fracture surface were studied by using the method of micro structure analysis, scanning, energy spectrum and electron microscope. The results show that Cu has effect on the hot ductility, and the hot ductility of 304hC stainless steel decrease with the increase of content of Cu. The deformation temperature also has much effect on the hot ductility, the suitable deformation temperature are 1100-1200℃. The reason of it is that the Cu rich chemical compounds were precipitated from austenite phase during cooling. The Cu rich chemical compounds are brittle substance such as Cu2S, Cu2O and ε-Cu etc.

关键词： 304hC stainless steel hot ductility brittle compounds precipi- tation mathematical model resistance to deformation

INFLUENCE OF hOT DEFORMATION ON CONTINUOUSCOOLING BAINITIC TRANSFORMATION IN A LOWCARBON STEEL

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Acta Metallurgica Sinica(English Letters) 1998年第2期11卷 121-127页

作者： Z.D.Wang J.B.Qu x.h.liu G.D.Wang Northeastern Univ Shenyang China

The influence of hot deformation conditions on continuous cooling bainitic transformation has been investigated for a low carbon microalloyed steel. The CCT diagrams show that deformation in unrecrpstallized austcnite ation can accelerate transformation process. Bainitic transformation in intermediate transformation temperature region is prominent, and the proeutectoid polygonal ferrite transformation at evelated high temperature is suppressed. According to optical and TEM analyses, low carbon bainitic ferrite is characterized by granular and lathlike ferrite, based on the cooling rate and deformation conditions. For nondeformation, groaps of coarse parallel ferrite lath form from the prior austenite grain boundaries with the same crystallographic orientation. For heavy deformaton, cell structure within the austenite grains due to the high dislocation density formed, which provides more nucleation sites for bainite ferrite. So deformation can discontinue the growth of ferrite laths and decrease the length of ferrite laths.

关键词： bainite continuous cooling transformation low carbon steel deformation

MODELLING FOR PREDICTION OF CONTINUOUS COOLING TRANSFORMATION KINETICS OF hOT-DEFORMED AUSTENITE STEEL

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Acta Metallurgica Sinica(English Letters) 1998年第3期11卷 225-229页

作者： J.B.Qu Z.D.Wang x.h.liu G.D.Wang Northeastern Univ Shenyang China

On the thermodynamics basis of regular solution sub-lattice model and soperelement model, kinetics basis of Cahn's transformation kinetics theory, and according to Scheil's additivity rule and eoperimental results obtained by thermal dilation method,a prediction model of transformations from hot-deformed austenite to ferrite, pearlite and bainite in low alloy steels, which could be applied to continuoas cooling process, is developed. The calculated transformed junctions of each phase based on laboratory controlled rolling and controlled cooling conditions in a low alloy steel are in reasonable agreement with the measured ones.

关键词： transformation kinetics thermodynamics continuous cooling,hot-deformed austenite

DEVELOPMENT OF NEW ThERMO-MEChANICAL SIMULATOR

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Acta Metallurgica Sinica(English Letters) 2004年第1期17卷 33-37页

作者： Z.G.Luo h.L.Su D.h.Zhang G.D.Wang x.h.liu The State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 ChinaThe State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 ChinaThe State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 ChinaThe State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 ChinaThe State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 China

A new multifunction thermo-mechanical simulator was successfully developed. The accuracy of measurement and control is very high through all digital control. More than twenty tests may be fulfilled including tension, compression, torsion, combination large deformation that meets the study of supersteel, etc. Its performance is introduced in the paper, such as designed ideas, machine structure, man-machine interface, control system, etc.

关键词： thermo-mechanical simulator multifunction control system combination large deformation

Microstructure evolution and shape memory behaviors of Ni_(47)Ti_(44)Nb_(9)alloy subjected to multistep thermomechanical loading with different prestrain levels

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Journal of Materials Science & Technology 2024年第4期171卷 80-93页

作者： Y.h.Zhang h.Li Z.W.Yang x.liu Q.F.Gu State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China Shaanxi Key Laboratory of high-Performance Precision Forming Technology and Equipment Northwestern Polytechnical UniversityXi’an 710072China

Ni_(47)Ti_(44)Nb_(9)shape memory alloy(SMA)is a promising material in the aerospace field due to its wide transformation *** application of shape memory effect depends on multistep thermomechan-ical loading,viz.,low-temperature deformation and subsequent heating to ***-temperature deformation prestrain plays a pivotal role in shape memory properties tailoring of SMA ***,microstructure evolution and deformation mechanisms of Ni_(47)Ti_(44)Nb_(9)SMA subjected to vari-ous prestrain levels are still *** this end,microstructure evolution and shape memory behaviors of Ni_(47)Ti_(44)Nb_(9)alloy subjected to multistep thermomechanical loading with prestrain levels of 8%-16%at-28℃(M_(s)+30℃)were *** results demonstrate that the stress-strain curve of the specimen exhibits four distinct stages at a maximal prestrain of 16%.Whereas stageⅡand stageⅢend at prestrains of∼8%and∼12%,*** stageⅡ,the stress-induced martensitic transformation is accompanied by the dislocation slip of the NiTi matrix andβ-Nb *** stageⅢ,in addition to the higher density of dislocations and further growth of stress-induced martensite variants(SIMVs),(001)compound twins are introduced as a result of the(001)deformation twinning in stress-induced ***{20-1}martensite twins are gradually introduced in stageⅣ.Correspondingly,after subsequent unloading and heating,a higher density of{114}austenite twins form in the specimen with a larger prestrain of 16%.With increasing prestrain from 8%to 16%,the recoverable strainε_(re)^(T)upon heating increases first and then ***ε_(re)^(T)obtains a maximum of 7.03%at 10%prestrain and de-creases to 6.17%at 16%*** increase ofε_(re)^(T)can be attributed to the formation of new SIMVs,the further growth of existing SIMVs,and the recoverable(001)compound *** the decrease ofε_(re)^(T)is mainly associated with the irrecoverable strain by{20−1}martensite *** effe

关键词： Ni_(47)Ti_(44)Nb_(9)shape memory alloy Wide transformation hysteresis Thermomechanical loading Microstructure evolution Shape memory behaviors Stress-induced martensitic transformation Deformation twinning

Progress on the antiferromagnetic topological insulator MnBi2Te4

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National Science Review 2024年第2期11卷 33-49页

作者： Shuai Li Tianyu liu Chang liu Yayu Wang hai-Zhou Lu x.C.xie hefei National Laboratory International Center for Quantum Materials School of Physics Peking University Institute for Nanoelectronic Devices and Quantum Computing Fudan University Department of Physics Harbin Institute of Technology Shenzhen Institute for Quantum Science and Engineering and Department of Physics Southern University of Science and Technology(SUSTech) Quantum Science Center of Guangdong-hong Kong-Macao Greater Bay Area(Guangdong) Shenzhen Key Laboratory of Quantum Science and Engineering International Quantum Academy Beijing Academy of Quantum Information Sciences Beijing Key Laboratory of Optoelectronic Functional Materials&Micro-Nano Devices Department of Physics Renmin University of China State Key Laboratory of Low Dimensional Quantum Physics Department of PhysicsTsinghua University Frontier Science Center for Quantum Information

Topological materials, which feature robust surface and/or edge states, have now been a research focus in condensed maTher physics. They represent a new class of materials exhibiting nontrivial topological phases,and provide a platform for exploring exotic transport phenomena, such as the quantum anomalous hall effect and the quantum spin hall effect. Recently, magnetic topological materials have attracted considerable interests due to the possibility to study the interplay between topological and magnetic *** particular, the quantum anomalous hall and axion insulator phases can be realized in topological insulators with magnetic order. MnBi2Te4, as the first intrinsic antiferromagnetic topological insulator discovered, allows the examination of existing theoretical predictions; it has been extensively studied, and many new discoveries have been made. here we review the progress made on MnBi2Te4from both experimental and theoretical aspects. The bulk crystal and magnetic structures are surveyed first, followed by a review of theoretical calculations and experimental probes on the band structure and surface states, and a discussion of various exotic phases that can be realized in MnBi2Te4. The properties of MnBi2Te4thin films and the corresponding transport studies are then reviewed, with an emphasis on the edge state transport. Possible future research directions in this field are also discussed.

关键词： MnBi2Te4 magnetic topological insulator antiferromagnetic quantum anomalous hall effect axion insulator

Terrestrial palynomorphs of the Cenozoic Pagodroma Group,northern Prince Charles Mountains, East Antarctica

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Terrestrial palynomorphs of the Cenozoic Pagodroma Group,nor...