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Tuning thermal expansion by a continuing atomic rearrangement mechanism in a multifunctional titanium alloy

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journal of Materials Science & Technology 2021年第21期80卷 234-243页

作者： D.l.Gong H.l.Wang E.G.Obbard S.j.li r.Yang Y.l.Hao Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang110016China School of Mechanical Engineering Dongguan University of TechnologyDongguan523808China Department of Electrical Engineering and Telecommunications University of New South WalesSydneyNSW2052Australia

As to multifunctional titanium alloys with high strength and low elastic modulus, thermal training is crucial to tune their thermal expansion from positive to negative, resulting in a novel linear expansion which is stable in a wide temperature range. Aided by the high-order Hooke's law of elastic solids,a reversible atomic rearrangement mechanism was proposed to explain the novel findings which are unexpected from typical shape memory alloys. To confirm this continuous mechanism, a Ti-Nb based alloy, which possesses a nanoscale spongy microstructure consisting of the interpenetrated Nb-rich and Nb-lean domains produced by spinodal decomposition, was used to trace the crystal structure change by in-situ high energy synchrotron X-ray diffraction analyses. By increasing exposure time, the overlapped diffraction peaks can be separated accurately. The calculated results demonstrate that, in the nanoscale Nb-lean domains, the crystal structure parameters vary linearly with changing temperature along the atomic pathway of the bcc-hcp transition. This linear relationship in a wide temperature range is unusual for first-order martensitic shape memory alloys but is common for Invar alloys with high-order spin transitions. Furthermore, the alloy exhibits smooth DSC curves free of transformation-induced heat peaks observed in shape memory alloys, which is consistent with the proposed mechanism that the reversible transition is of high-order.

关键词： Coefficient of thermal expansion Multifunctional titanium alloys Spongy microstructure Atomic rearrangement Elastic anisotropy

Analysis of antisym metric cross-ply laminates using high-order shear deformation theories:a meshless approach

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Acta Mechanica Sinica 2020年第5期36卷 1078-1098,I0003页

作者： D.E.S.rodrigues j.Belinha l.M.j.S.Dinis r.M.Natal jorge Institute of Science and Innovation in Mechanical and Industrial Engineering 4200-465 PortoPortugal Department of Mechanical Engineering School of EngineeringPolytechnic of Porto(ISEP)4200-072 PortoPortugal Department of Mechanical Engineering Faculty of EngineeringUniversity of Porto(FEUP)4200-465 PortoPortugal

For many years finite element method(FEM)was the chosen numerical method for the analysis of composite ***,in the last 20 years,the scientific community has witnessed the birth and development of several meshless methods,which are more flexible and equally accurate numerical *** meshless method used in this work is the natural neighbour radial point interpolation method(NNrPIM).In order to discretize the problem domain,the NNrPIM only requires an unstructured nodal ***,using the Voronoi mathematical concept,it enforces the nodal connectivity and constructs the background integration *** NNrPIM shape functions are constructed using the radial point interpolation *** this work,the displacement field of composite laminated plates is defined by high-order shear deformation *** the end,several antisymmetric cross-ply laminates were analysed and the NNrPIM solutions were compared with the *** obtained results show the efficiency and accuracy of the NNrPIM formulation.

关键词： Antisymmetric cross-ply laminates High-order shear deformation theories Meshless methods Naturalneighbour radial point interpolation method(NNrPIM)

Phase Control of Transient Optical Properties of Double Coupled Quantum-Dot Nanostructure via Gaussian laser Beams

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Chinese Physics letters 2018年第2期35卷 29-33页

作者： j.Shiri F.Shahi M.r.Mehmannavaz l.Shahrassai Young researchers and Elite Club Tabriz BranchIslamic Azad University Department of Atomic and Molecular Physics University of Tabriz Young researchers and Elite Club Mashhad BranchIslamic Azad University

We theoretically analyze the transient properties of a probe field absorption and dispersion in a coupled semiconductor double-quantum-dot *** show that in the presence of the Gaussian laser beams,absorption and dispersion of the probe field can be dramatically influenced by the relative phase between applied fields and intensity of the Gaussian laser *** and steady-state behaviors of the probe field absorption and dispersion are discussed to estimate the required switching *** estimated range is between 5-8 ps for subluminal to superluminal light propagation.

关键词： Phase Control of Transient Optical Properties of Double Coupled Quantum-Dot Nanostructure via Gaussian laser Beams QDs

Preparation of neodymium-doped yttrium aluminum garnet powders and fibers

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journal of rare Earths 2008年第5期26卷 670-673页

作者： r. lópez j. Zárate E. A. Aguilar j. Muoz-Saldaa Instituto de Investigaciones Metalurgicas UMSNH Morelia Centro de Investigación y de Estudios Avanzados del IPN Unidad Queretaro

Using nitrate precursors, a novel spray-drying assisted citrate gel process for the preparation of neodymium-doped yttrium alumi- num garnet （YAG） phase was developed. Synthesis of single-phase polycrystalline YAG was achieved at temperatures as low as 800 ℃ using the spray-drying methodology whilst conventional approaches currently available require 1000 ℃. Initially, a solution was prepared by mixing aluminum and yttrium nitrates, citric acid, etilenglycol and neodymium oxide. This solution was dried by pulverization （spray dryer） to obtain aggregated precursor powders of the compound. These aggregates were calcined at 800, 850 and 900 ℃ to determine the phase evolution from amorphous to crystalline by X-ray diffraction （XrD）. The morphology of aggregates was characterized by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Moreover, through XrD it was determined that the crystallization of YAG phase started at about 800 ℃ without any intermediate phases. The powders were composed of spherical aggregates with an average diameter of 1 um. From these powders, ceramic fibers with additions of 2at.% and 5at.% Nd, were extracted from the melt with diameters ranging from 30 um to 50 um.

关键词： spray-drying melt extraction fibers yttrium aluminum garnet rare earths

Structural Ultrafine Grained Steels Obtained by Advanced Controlled rolling

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journal of Iron and Steel research International 2013年第1期20卷 62-70页

作者： r González j O García M A Barbés M j Quintana l F Verdeja j I Verdeja School of Engineering Panamerican UniversityMexico City 03920Mexico E T S I M O Oviedo UniversityOviedo 33004Spain

Steels with ultrafine grains （lower than 5 μm）, which usually known as ultrafine ferrite or ultrafine grained materials, are presently the object of intense research, because of the improvement in resistance and fracture toughness they may reach compared to conventional steels （with grain sizes above this value）. It is shown that the forenamed steels designated in the Euronorm EN 10149-2, which are manufactured by advanced techniques of controlled rolling and mainly used in automotive industry, have an ultrafine grain size in the range of 2.5 to 3.5 μm, and with elastic yield stresses higher than 400 MPa. Based on the Morrison-Miller criterion, it is shown that values of the strain-hardening coefficient lower than 0.08 would make the industrial application of these steels unfeasible.

关键词： ultrafine grained steel mechanical property manufacturability strain-hardening

Ultrafine Grained HSlA Steels for Cold Forming

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journal of Iron and Steel research International 2010年第10期17卷 50-56页

作者： r González j O García M A Barbés M j Quintana l F Verdeja j I Verdeja School of Engineering Panamerican University ETSIMO Oviedo University

The industrial level production of ultrafine grained （or ultrafine ferrite） ferrous alloys was investigated through three examples of steels that complied with the EN 10149-2 Euronorm and were produced by advanced con- trolled hot rolling techniques. The steel samples were tension tested and chemically analyzed, and the microstructure was evaluated through quantitative metallographic techniques to determine parameters such as yield stress, amount of microalloying elements, strain hardening coefficient, grain size, and grain size distribution. These steels were micro- alloyed with Ti, Nb, and Mn with ASTM grain sizes of approximately 13--15. The careful control of chemical com- position and deformation during production, giving a specific attention to the deformation sequences, austenite non- reerystallization temperatures and allotropic transformations during cooling, are indispensable to obtain steels with an adequate strain hardening coefficient that allows cold working operations such as bending, stretching or drawing.

关键词： ultrafine steel metallography strain hardening Euronorm

Enhancements to Modified Chebyshev-Picard Iteration Efficiency for Perturbed Orbit Propagation

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Computer Modeling in Engineering & Sciences 2016年第1期111卷 29-64页

作者： B.Macomber A.B.Probe r.Woollands j.read j.l.junkins Texas A&M University College StationTXUSA.

Modified Chebyshev Picard Iteration is an iterative numerical method for solving linear or non-linear ordinary differential *** a serial computational environment the method has been shown to compete with,or outperform,current state of practice numerical *** paper presents several improvements to the basic method,designed to further increase the computational efficiency of solving the equations of perturbed orbit propagation.

关键词： Astrodynamics Orbit Propagation Cheybshev Polynomials Picard Iteration.

Deformation behaviors of as-built and hot isostatically pressed Ti-6Al-4V alloys fabricated via electron beam rapid manufacturing

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journal of Materials Science & Technology 2019年第11期35卷 2552-2558页

作者： Z.liu Z.B.Zhao j.r.liu l.Wang S.X.Zhu G.Yang S.l Gong Q.j.Wang r.Yang institute of metal research chinese academy of sciencesshenyang110016china school of materials science and engineering university of science and technology of chinahefei230000china avic manufacturing technology institute beijing100024china

The deformation behavior of as-built and hot isostatically pressed(HIP)Ti-6Al-4V alloys fabricated using electron beam rapid manufacturing(EBrM)were investigated in this *** deformation characteristics were characterized using a laser scanning confocal microscope and electron back-scattered diffraction(EBSD).In the as-built sample,prismatic slip was the main mode of deformation,as well as a small amount of basal slip and *** planar slip lines with large length scales were observed across severalα*** hot isostatical pressing,prismatic and basal slip were the main mode of deformation,accompanied by abundant cross-slip and multiple slip,and most of the slip lines were blocked within an a *** differences in deformation behavior were associated with the coarsening of a laths and the more retained p phase after HIP compared to the as-built *** cross-slip and multiple slip can lead to superior elongation-to-failure and a greater strain hardening effect in the HIP alloy compared to the as-built sample.

关键词： Electron beam rapid manufacturing Ti-6Al-4V Hot isostatic pressure Mechanical properties Slip behavior

STUDY ON NUMErICAl SIMUlATION OF CASTING THErMAl STrESSES BASED ON FDM

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Acta Metallurgica Sinica(English letters) 2004年第1期17卷 7-10页

作者： j.j.Yan l.l.Chen D.M.liao H.T.lin r.X.liu College of Materials Huazhong University of Science and TechnologyWuhan 430074ChinaMechanic DepartmentThe University of Iowa Iowa CityIA 52246USACollege of MaterialsHuazhong University of Science and TechnologyWuhan 430074ChinaCollege of MaterialsHuazhong University of Science and TechnologyWuhan 430074ChinaCollege of MaterialsHuazhong University of Science and TechnologyWuhan 430074China

A system for the numerical simulation of 3D temperature and stress fields during casting process was studied, developed and practiced based on finite difference method (FDM) in this paper. An approach where the stress/strain and the heat transfer analysis use the same computational domain was presented, which avoided transferring temperature data between FDM and FEM nodes and elements. A slot-board steel casting was simulated and the calculated results are in agreements with those obtained from practical producing.

关键词： thermal stress field numerical simulation FDM