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Modified Joint distribution of Wave Heights and Periods

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China Ocean Engineering 2016年第3期30卷 359-374页

作者： H.d.zhang C.Guedes Soares Centre for Marine Technology and Ocean Engineering (CENTEC) Instituto Superior Técnico Universidade de Lisboa

The modified versions of the linear theoretical model of Longuet-Higgins （1983） are derived in this work and also compared with the laboratory experiments carried out in MAR1NTEK. The main feature of modifications is to replace the mean frequency in the formulation with the peak frequency of the wave spectrum. These two alternative forms of joint distributions are checked in three typical random sea states characterized by the initial wave steepness. In order to further explore the properties ＆these models, the associated marginal distributions of wave heights and wave periods are also researched with the observed statistics and some encouraging results are obtained.

关键词： Longuet-Higgins joint distribution mixed sea state nonlinear wave series wave height wave period

A strong and ductile NiCoCr-based medium-entropy alloy strengthened by coherent nanoparticles with superb thermal-stability

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Journal of Materials Science & Technology 2023年第1期132卷 201-212页

作者： d.d.zhang J.Kuang H.Xue J.Y.zhang G.Liu J.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China

In this work,we designed a novel NiCoCr-based medium-entropy alloy(MEA)strengthened by coher-ent L12-nanoparticles,i.e.,(NiCoCr)92 Al 6 Ta 2(at.%).The strengthening and deformation mechanisms of the material and the coarsening kinetics of the coherent precipitates were systematically *** results indicated that giant precipitation hardening and its synergy with other strengthening contributors confer on the aged material a yield strength as high as 1.0 ***,a unique particle-features-dependent plasticity mechanism was revealed in this *** is,the alloy with a lower volume frac-tion,denser distribution,and finer particles mainly deformed by dislocation planar slip,otherwise,stack-faults-mediated plasticity was favored,rationalized by the cooperative/competitive effect of stack-fault energy,spatial confinement,and applied ***,the coarsening behavior of precipitate fol-lowed a modified Lifshitz-Slyozov-Wagner(LSW)model,and the nanoparticles displayed remarkably su-perior thermal stability compared to most traditional superalloys and reported multicomponent *** superb coarsening resistance of precipitate originated from the coupled effect of intrinsic sluggish diffusion in multi-principal alloys and the dual-roles of Ta species as a precipitate *** work provides a new pathway to develop strong-yet-ductile multicomponent alloys as promising candidates for high-temperature applications.

关键词： Medium-entropy alloy Mechanical properties Precipitation hardening deformation mechanisms Coarsening kinetics

Achieving excellent strength-ductility synergy in twinned NiCoCr medium-entropy alloy via Al/Ta co-doping

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维普期刊数据库

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Journal of Materials Science & Technology 2021年第28期87卷 184-195页

作者： d.d.zhang H.Wang J.Y.zhang H.Xue G.Liu J.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an710049PR China Science and Technology on Reactor Fuel and Materials Laboratory Nuclear Power Institute of ChinaChengdu610041PR China

Alloying is an effective strategy to tailor microstructure and mechanical properties of metallic materials to overcome the strength-ductility trade-off *** this work,we combined a novel alloy design principle,*** pronounced solid solution hardening(SSH)based on the misfit volumes engineering,and simultaneously,architecting the ductile matrix based on the valence electron concentrations(VEC)criterion,to fulfill an excellent strength-ductility synergy for the newly emerging high/medium-entropy alloys(HEAs/MEAs).Based on this strategy,Al/Ta co-doping within NiCoCr MEA leads to an efficient synthetic approach,that is minor Al/Ta co-doping not only renders significantly enhanced strength with notable SSH effect and ultrahigh strain-hardening capability,but also sharply refines grains and induces abnormal twinning behaviors of(NiCoCr)_(92)Al_(6)Ta_(2) *** with the partially twinned NiCoCr MEA,the yield strength(σy)and ultimate tensile strength(σUTS)of fully twinned Al/Ta-containing MEA were increased by~102%to~600 MPa and~35%to~1000 MPa,respectively,along with good ductility beyond 50%.different from the NiCoCr MEA with deformation twins(dTs)/stacking faults(SFs)dominated plasticity,the extraordinary strain-hardening capability of the solute-hardened(NiCoCr)_(92)Al_(6)Ta_(2) MEA,deactivated deformation twinning,originates from the high density of dislocation walls,microbands and abundance of *** abnormal twinning behaviors,i.e.,prevalence of annealing twins(ATs)but absence of dTs in(NiCoCr)_(92)Al_(6)Ta_(2) MEA,are explained in terms of the relaxation of grain boundaries(for ATs)and the twinning mechanism transition(for dTs),respectively.

关键词： Medium-entropy alloys Mechanical properties Solid solution hardening Twinning behavior Strength-ductility synergy

RELATIONSHIP BETWEEN INFRAREd RAdIATION ANd CRYSTAL STRUCTURE IN Fe-Mn-Co-Cu-O SPINELS

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Acta Metallurgica Sinica(English Letters) 2008年第1期21卷 15-20页

作者： Y. zhang d.J. Wen School of Material Engineering Soochow University Suzhou 215021 China

Ni^3＋ and Cr^3＋ doped Fe-Mn-Co-Cu-O spinels have been prepared by solid phase sintering. The valence states and distribution of transition ions in the spinel crystals are inferred by the consideration of thermodynamic principle and crystalline field theory. The mierostructure and performance of those are studied by X-ray diffraction （XRd）, Fourier transform infrared （FT-IR）, and IRE-2 infrared radiant instrument. Ni3＋ and Cr3＋ occupy the vacancies or substitute the other ions in the spinel structures and form diverse spinel structures, which exhibit infrared integral emissivities of 0.93 in the whole band, and 0. 94 in the band within 14-25μm too. The content of Fe2O3 and MnO2 in the spinel crystals changes, maybe it induces infrared radiativity of spinels differently.

关键词： Crystal structure Mineral Infrared radiation property

Caustic Failure of Thermal Insulated Tubing in Steam Flooding

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Journal of Materials Science & Technology 1997年第1期13卷 27-36页

作者： Xian, AP San, YY zhang, d Wang, YK Sun, HP LIAOHE OIL FIELd MACHINERY PLANT PANJIN 124209PEOPLES R CHINA

The coupling of the pre-stressed thermal insulated tubing string broke down inside the steam flooding welts, after the tubing were used in high temperature and high pressure steam for about two years. With further check, it was found that most of the weld joints between the inner and outer tubing also cracked. The failure analysis for the accidents has been carried out by the analysis of chemical composition for the steels, microstructure observation, mechanical property tests, and the investigation of the service environment etc.. The results show that the early damage of the pre-stressed thermal insulated tubing string is mainly induced by the caustic stress corrosion, which can be strengthened by an unstable microstructure of the coupling serviced at high temperature for a long time. Moreover, the high pre-stress design on the thermal insulated pipe for the cyclic steam injection may be not suitable to the situation of steam flooding, which would result in the weld joint cracking.

关键词： Steel pipe

<110> Fiber Texture Evolution of Ferrite Wires during drawn-torsion and drawn-annealing-torsion Process

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Journal of Materials Science & Technology 2012年第11期28卷 1010-1014页

作者： Y.d. Liu Y.d. zhang A. Tidul L. Zuo Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education) Northeastern University Shenyang110004 China Letam/Isgmp CNRS Metz 57000 France

In this paper, the texture and microstructure evolution of drawn-torsion and drawn-annealing-torsion ferrite wires are studied by electron back scattering diffraction （EBSd） in order to investigate the special torsion texture evolution. Compared to the simulation results, the stable texture components {110}〈 110 〉 and {110}〈112〉 in both drawn-torsion and drawn-annealing-torsion wires display different evolution processes. The texture of the drawn-annealing-torsion wire fits to the Taylor model. A special texture evolution is found in drawn-torsion wires, related to the grain shape, and the heterogeneous deformation. A new plastic deformation viewpoint is suggested based on the special microstructure of drawn ferrite wire.

关键词： Texture Electron back scattering diffraction (EBSd) Torsion Plastic deformation

Structure and Magnetic Properties of Boron-oxide and Boron-nitride Coated Iron Nanocapsules

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Journal of Materials Science & Technology 2010年第11期26卷 1051-1056页

作者： W.S. zhang J.G. Zheng E. Briick P.Z. Si d.Y. Geng Z.d. zhang Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences China and International Centre for Materials Physics Chinese Academy of Sciences Shenyang 110016 China College of Physics & Electronic Engineering Taizhou University Taizhou 317000 China Electron Probe Instrumentation Center (EPIC) Northwestern University 2225N Campus Drive 1156 MLSF Evanston IL 60208-3108 USA Van der Waals-Zeeman Instituut Universiteit van Amsterdam Valckenierstraat 65 1018 XE Amsterdam The Netherlands

The boron-oxide coated iron nanocapsules have been prepared by arc-discharge in a mixture of diborane and nitrogen,and then the boron-nitride coated iron nanocapsules by a subsequent annealing under a nitrogen atmosphere at 1100 ℃.After the arc-discharge,the boron-oxide coated iron nanocapsules form,which show an amorphous surface layer of B2O3 （and/or B） and a core of γ-Fe,α-Fe,FeB *** being annealed,part of the α-Fe phase transforms to the γ-Fe phase,and the FeB phase decomposes while the BN phase *** BN shell structure formed in the BN encapsulating iron nanocapsules is *** properties of the boron-oxide coated and the boron-nitride coated iron nanocapsules were compared and discussed in terms of the particles sizes,the phase components,and the surface structures.

关键词： Arc discharge Nanocapsules Magnetic properties

designing hetero-structured ultra-strong and ductile Zr-2.5Nb alloys:Utilizing the grain size-dependent martensite transformation during quenching

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Journal of Materials Science & Technology 2022年第30期125卷 198-211页

作者： S.Y.Liu J.Y.zhang J.Kuang X.Y.Bao d.d.zhang C.L.zhang J.K.Yang G.Liu J.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China

To further improve the service performance of Zr-2.5Nb alloy worked as pressure tubes in pressurized heavy water reactors,more investigation about the microstructure and thermomechanical processing route of Zr-2.5Nb alloy need to be *** this work,a hetero-structured Zr-2.5Nb alloy was prepared by applying a novel *** analysis reveals that the alloy exhibits a grain sizedependent martensite substructure transition during post-rolling *** hetero-structure consists of equiaxed primaryαgrains and the lamellae groups containing both parallelα’dislocation martensite andα’twin *** with the previously reported Zr-Nb alloys,the present Zr-2.5Nb alloys manifest the highest yield strength(∼710 MPa),together with a high ultimate tensile strength(∼844 MPa)and good ductility(∼17.1%).The enhanced mechanical properties are found to arise from the properly controlled fraction/size of the two types of martensite,which not only significantly strengthens the alloy but also contributes to a stronger strain hardening.A model based on the grain-size-dependent critical resolved shear stress for dislocation slip and twinning has been proposed to explain theα’martensite substructures transition at a critical grain size dc=3.3μ*** this size,the critical resolved shear stress(CRSS)for twinning is higher than that for the***,theα’dislocation martensite is more favorable to ***,theα’twin martensite would exhibit a high *** present work indicates that making use of the grain size-dependent martensite transformation to tailor the heterostructure in Zr alloys is an effective strategy to overcome the strength–ductility trade-off in the material.

关键词： Zr-Nb alloys Heterogeneous structure Martensitic transformation Grain size Strength

SIMULATION OF VIBRATION STRESS RELIEF AFTER WELdING BASEd ON FEM

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Acta Metallurgica Sinica(English Letters) 2008年第4期21卷 289-294页

作者： X.C. Zhao Y.d. zhang H.W. zhang Q. Wu School of Mechanical Engineering and Automation Beijing University of Aeronautics and Astronautics Beijing 100083 China State Key Laboratory of Virtual Reality Technology Beijing University of Aeronautics and AstronauticsBeijing 100083 China

A finite element model is developed for the simulation of vibration stress relief （VSR） after welding. For the nonresonant vibration, the reduction in stress strongly depends on the amplitude of vibration. For the resonant vibration, the vibration frequency is the key for stress relief. The vibration frequency should be close to the structure natural frequency for the desired vibration mode. Only small vibration amplitude is required, which will be amplified during vibration. Vibration time does not have a major impact on vibration stress relief. When the amplitude of vibration stress relief is large, the treatment will be more effective.

关键词： Residual stress Vibration stress relief Simulation