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Journal of Materials Science & Technology 2022年第5期100卷 246-253页

作者： J.F.Zhao h.P.wang B.Wei School of physical Science and Technology Northwestern Polytechnical UniversityXi’an 710072China

A new intermetallic compound of thermodynamically stable Nb_(2)Ni phase is discovered within Nb-Ni binary system,refreshing the current situation that there are only three stable intermediate phases of Nb_(7)Ni_(6),NbNi_(3) and NbNi_(8).The new stable phase is generated from the peritectoid transition:(Nb)+Nb_(7)Ni_(6)→Nb_(2)Ni,and the transformation temperature is 1533 K.This refreshes the current equilibrium Nb-Ni binary phase diagram.It is confirmed by transmission electron microscopy and the annealing experiments,which is determined to be the FCC structure(pearson:cF96,space grope:Fd-3m O2,a=11.888A).Furthermore,the equilibrium properties of Nb_(2)Ni phase are produced by density functional theory,including the formation energy,cohesive energy,bulk modulus and lattice constant.

关键词： Intermetallic compound peritectoid transition Transmission electron microscopy Density functional theory Nb alloy

primary dendrite growth kinetics and rapid solidification mechanism of highly undercooled Ti-Al alloys

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Journal of Materials Science & Technology 2020年第5期40卷 47-53页

作者： Z.C.Luo h.P.wang Department of Applied physics Northwestern Polytechnical UniversityXi’an 710072China

The rapid solidification processes of undercooled Ti-(47,50,54)at.%Al alloys were investigated by electromagnetic levitation(EML)method combined with a high-speed photoelectric detector.The maximum undercoolings of the three liquid alloys were 376 K,352 K and 316 K,respectively.Recalescence processes corresponding to the primary dendrite growth and subsequent phase transition were recorded at various undercoolings.The primary dendrite growth velocity V meets a double exponential relationship with the undercooling T.Besides,a novel formula with physical meaning is proposed to explain that the more ordered liquid metal atoms accelerate the primary dendrite growth.Three recalescences are found at all undercoolings for Ti-47 at.%Al alloy and at high undercoolings for Ti-50 at.%Al alloy.The microstructures of solidified Ti-47 at.%Al alloys successively appear as coarse lamellar dendrites and finally evolve to refined parallel lamellar dendrites with the increasing undercooling.When T rises,the microstructures of solidified Ti-50 at.%Al alloys appear from coarse primary dendrites and interdendritic dendrites to refined lamellar dendrites.In the process from low undercooling to high undercooling,the primary phase of undercooled Ti-54 at.%Al alloys changes from r-Ti(r)to r-TiAl(r)and the microstructures of solidified alloys evolve from spherical primary dendrites and matrix phases to cellular dendrite phases.Meanwhile,for the Ti-(47,50)at.%Al,the transformation temperature of metastable intermediateγphase decreases with the increase of undercooling.Moreover,the microhardness of the three solidified alloys reaches the maximum when the undercoolings are 185 K,270 K and 316 K,respectively.

关键词： Electromagnetic levitation Rapid solidification Dendrite growth Microstructure Microhardness

Rapid Growth of TiNi intermetallic compound within undercooled Ti_(50)Ni_(50)alloy under electrostatic levitation condition

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Journal of Materials Science & Technology 2021年第18期77卷 82-89页

作者： p.F.Zou C.h.Zheng L.hu h.P.wang School of physical Science and Technology Northwestern Polytechnical University.Xi'an710072China

The undercooling dependence of the solidification mechanism was systematically explored by the electrostatic levitation(ESL)facility.During the experiments,the maximum undercooling reached up to 406 K(0.26 T_L)and the growth velocity of the primary TiNi phase was in-situ determined at various undercoolings.At the initial increase of alloy undercooling,the value of growth velocity sluggishly rose followed by a power function.In this case,the primary TiNi phase preferentially developed as the equiaxed dendrite,then the remnant liquid participated as Ti_(2)Ni andα-Ti phases on the grain boundary.Once the undercooling exceeded the critical value of 350 K,the growth velocity of the primary phase displayed a sharply increase tendency.Meanwhile,the TEM results demonstrated that the precipitation of the intermetallic Ti_(2)Ni compound was gradually restrained during the rapid solidification and the R-phase existing in the TiNi matrix at large undercooling implied that the martensitic transformation was incomplete.

关键词： Undercooling Ti-Ni alloy Solidification Growth kinetics

Density determination and simulation of Inconel 718 alloy at normal and metastable liquid states

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Journal of Materials Science & Technology 2018年第3期34卷 436-439页

作者： h.P.wang C.h.Zheng p.F.Zou S.J.Yang L.hu B.Wei Department of Applied physics Northwestern Polytechnical University

The density of liquid Incone1718 alloy was experimentally measured by electrostatic levitation technique, where the maximum undercooling of 100 K was realized for the commercial sample. The measured density of liquid lnconel 718 alloy is 7.39 g cm^-3 at the liquidus temperature of 1663 K which was confirmed by DSC experiment, with the linear temperature coefficient of -6.89 × 10^-4 gcm^-3 K^-1. Correspondingly, four ternary Ni-Cr-Fe compositions were designed to simulate the density of liquid lnconel 718 alloy with 16000 atoms, from which the liquid structure is revealed by pair distribution function, The predicted result shows a remarkable enhancement with the decrease of temperature at the first neighbor distance.

关键词： Undercooling Density Liquid metal and alloy Levitation

pulsed Microfluid Force-Based On-Chip Modular Fabrication for Liver Lobule-Like 3D Cellular Models

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Cyborg and Bionic Systems 2021年第1期2021卷 222-233页

作者： J.Cui h.P.wang Q.Shi T.Sun Science and Technology on Electronic Test and Measurement Laboratory North University of ChinaTaiyuan 030051China Intelligent Robotics Institute School of Mechatronical EngineeringBeijing Institute of TechnologyBeijing 100081China Beijing Advanced Innovation Center for Intelligent Robots and Systems Beijing Institute of TechnologyBeijing 100081China Key Laboratory of Biomimetic Robots and Systems(Beijing Institute of Technology) Ministry of EducationBeijing 100081China

In vitro three-dimensional(3D)cellular models with native tissue-like architectures and functions have potential as alternatives to human tissues in regenerative medicine and drug discovery.however,it is difficult to replicate liver constructs that mimic in vivo microenvironments using current approaches in tissue engineering because of the vessel-embedded 3D structure and complex cell distribution of the liver.This paper reports a pulsed microflow-based on-chip 3D assembly method to construct 3D liver lobule-like models that replicate the spatial structure and functions of the liver lobule.The heterogeneous cell-laden assembly units with hierarchical cell distribution are fabricated through multistep photopatterning of different cell-laden hydrogels.Through fluid force interaction by pulsed microflow,the hierarchical assembly units are driven to a stack,layer by layer,and thus spatially assemble into 3D cellular models in the closed liquid chamber of the assembly chip.The 3D models with liver lobule-like hexagonal morphology and radial cell distribution allow the dynamic perfusion culture to maintain high cell viability and functional expression during long-term culture in vitro.These results demonstrate that the fabricated 3D liver lobule-like models are promising for drug testing and the study of individual diagnoses and treatments.

关键词： culture maintain spatially

Releasing the residual stress of C_(f)/SiC-Gh3536 joint by designing an Ag-Cu-Ti+Sc_(2)(WO_(4))_(3) composite filler metal

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Journal of Materials Science & Technology 2022年第13期108卷 102-109页

作者： p.wang X.Liu h.wang J.Cao J.Qi J.Feng State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China

Due to native character of thermal expansion coefficient(CTE)mismatch between C_(f)/SiC and Gh3536,achieving high strength joint was a huge challenge for C_(f)/SiC-Gh3536 joints.herein,a composite filler metal of Ag-Cu-Ti+Sc_(2)(WO_(4))_(3) was developed to join C_(f)/SiC and Gh3536.This work introduced Sc_(2)(WO_(4))_(3) to Ag-Cu-Ti system as a negative thermal expansion(NTE)reinforcing phase to release joint residual stress.Sc_(2)(WO_(4))_(3) was evenly distributed in the brazing seam and reacted with Ti to form Ti_(3)O_(5) reaction layer.The results of finite element analysis showed that the residual stress of the joints was effectively released by introducing Sc_(2)(WO_(4))_(3) reinforcing phase,and the mises stress was decreased from447 to 401 Mpa.The maximum shear strength of the C_(f)/SiC-Gh3536 joint brazed with Ag-Cu-Ti+6 vol%Sc_(2)(WO_(4))_(3) filler alloys was 64 Mpa,which was about 2.6 times higher than that of Ag-Cu-Ti alloys.The results of this study provide a promising strategy for the introduction of new Sc_(2)(WO_(4))_(3) reinforcing phase in Ag-Cu-Ti system,and improve the reliability and feasibility of composite brazing alloy in brazing filed.

关键词： Negative thermal expansion Brazing Residual stress Composite brazing alloy CTE

Analyzing the Effects of Key Design Factors of a Negative-Differential-Resistance(NDR)Microfluidic Oscillator–an Equivalent-Circuit-Model Approach

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Advances in Applied Mathematics and Mechanics 2022年第6期14卷 1381-1399页

作者： J.W.Wu h.M.Xia Z.p.wang W.wang h.J.Du School of Mechanical Engineering Nanjing University of Science and TechnologyNanjingJiangsu 210094China Singapore Institute of Manufacturing Technology 73 Nanyang DriveSingapore 637662Singapore School of Mechanical and Aerospace Engineering Nanyang Technological University50 Nanyang AvenueSingapore 639798Singapore

Numerical study on dynamic hydroelastic problems is usually rather complex due to the coupling of fluid and solid mechanics.here,we demonstrate that the performance of a hydroelastic microfluidic oscillator can be analyzed using a simple equivalent circuit model.previous studies reveal that its transition from the steady state to the oscillation state follows the negative-differential-resistance(NDR)mechanism.The performance is mainly determined by a bias fluidic resistor,and a pressurevariant resistor which further relates to the bending stiffness of the elastic diaphragm and the depth of the oscillation chamber.In this work,a numerical study is conducted to examine the effects of key design factors on the device robustness,the applicable fluid viscosity,the flow rate,and the transition pressure.The underlying physics is interpreted,providing a new perspective on hydroelastic oscillation problems.Relevant findings also provide design guidelines of the NDR fluidic oscillator.

关键词： Microfluidic oscillator hydroelastics equivalent circuit model negative differential resistance

Effect of grain size on the intrinsic mechanical stability of austenite in transformation-induced plasticity steels:The competition between martensite transformation and dislocation slip

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Journal of Materials Science & Technology 2023年第31期162卷 38-43页

作者： D.p.Yang T.wang Z.T.Miao p.J.Du G.D.wang h.L.Yi State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China

The deformation accompanied by austenite to martensite trans-formation was first studied in Fe-Ni alloys,high-Mn steels,and austenitic stainless steels with a full austenite microstructure.The plasticity of these steels can be improved by the trans-formation during deformation and hence they were named as transformation-induced plasticity(TRIp)steels[1].Over the past few decades,a series of TRIp steels with multiphase microstructure for automotive applications were developed.These steels contain-ing a certain amount of austenite were called TRIp-assisted steels,such as low-alloy TRIp steels[2],carbide-free bainitic steels[3],δ-TRIp steels[4],quenching and partitioning steels[5],and medium-Mn steels[6].The mechanical property of TRIp steels is largely determined by the mechanical stability of austenite[7]which de-pends on the chemical composition[8],grain size[9],orientation[10],and morphology[11]of austenite grains,as well as the nature of neighboring phases[12].In most cases of TRIp-assisted steels,larger austenite grains transform to martensite earlier or faster than smaller austenite grains with the increase of macrostrain[13-18],indicating lower mechanical stability.however,larger austen-ite grains usually contain less C and Mn[13,17-19]and suffer more strain than smaller grains during deformation[20],it doesn’t mean that grain refinement increases the mechanical stability of austen-ite.

关键词： austenite martensite transformation

predictive fatigue crack growth law of high-strength steels

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Journal of Materials Science & Technology 2022年第5期100卷 46-50页

作者： h.F.Li p.Zhang B.wang Z.F.Zhang Laboratory of Fatigue and Fracture for Materials Shi-changxu Innovation Center for Advanced MaterialsChinese Academy of SciencesInstitute of Metal ResearchShenyang 110016China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuang 050043China

The fatigue resistance of metallic materials is generally attributed to both strength and toughness.Unfortunately,these properties are mutually exclusive in most materials.Classical theories like paris’law only provide some data correlation schemes rather than a predictive capability,which cannot satisfactorily guide the anti-fatigue design.In this study,for the first time,the predictive fatigue crack growth rate law is proposed by considering the effects of both strength and toughness.Accordingly,a quantitative criterion is established for judging the fatigue crack resistance of high-strength steels.The predictive law would provide a unique view to the quantitative anti-fatigue design of metallic materials.

关键词： Fatigue crack growth Strength and toughness paris’law high-strength steels

Thermoelectric field for a coated hole of arbitrary shape in a nonlinearly coupled thermoelectric material

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Applied Mathematics and Mechanics(English Edition) 2022年第11期43卷 1691-1700页

作者： Xu wang p.SChIAVONE School of Mechanical and power Engineering East China University of Science and TechnologyShanghai 200237China Department of Mechanical Engineering University of Alberta10-203 Donadeo Innovation Center for EngineeringEdmonton T6G 1H9Canada

We study the thermoelectric field for an electrically and thermally insulated coated hole of arbitrary shape embedded in an infinite nonlinearly coupled thermoelectric material subject to uniform remote electric current density and uniform remote energy flux.A conformal mapping function for the coating and matrix is introduced,which simultaneously maps the hole boundary and the coating-matrix interface onto two concentric circles in the image plane.Using analytic continuation,we derive a general solution in terms of two auxiliary functions.The general solution satisfies the insulating conditions along the hole boundary and all of the continuity conditions across the perfect coating-matrix interface.Once the two auxiliary functions have been obtained in the elementary-form,the four original analytic functions in the coating and matrix characterizing the thermoelectric fields are completely and explicitly determined.The design of a neutral coated circular hole that does not disturb the prescribed thermoelectric field in the thermoelectric matrix is achieved when the relative thickness parameter and the two mismatch parameters satisfy a simple condition.Finally,the neutrality of a coated circular thermoelectric inhomogeneity is also accomplished.

关键词： thermoelectric material nonlinear coupling coated hole of arbitrary shape complex variable method analytic solution neutral coated hole