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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 thec+a>***,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

dislocation self-interaction in TiAl:Evolution of super-dislocation dipoles revealed by atomistic simulations

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Journal of Materials Science & Technology 2021年第10期69卷 138-147页

作者： Z.Zhen H.Wang c.y.Teng c.G.Bai d.S.Xu R.yang Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of China.Shenyang 110016China School of Materials Science and Engineering University of Shanghai for Science and TechnologyShanghai 200093China Laboratory of Fundamental Research AVIC China Aero-Polytechnology EstablishmentBeijing 100028.China

As one of the fundamental outcomes of dislocation self-interaction,dislocation dipoles have an important influence on the plastic deformation of materials,especially on fatigue and *** this work,superdislocation dipoles inγ-TiAl andα_(2)-Ti_(3)Al were systematically investigated by atomistic simulations,with a variety of dipole heights,orientations and annealing tempe *** results indicate that non-screw super-dipoles transform into locally stable dipolar or reconstructed cores at low temperature,while into isolated or interconnected point defect clusters and stacking fault tetrahedra at high temperature via short-range diffu ***-screw super-dipoles inγ-TiAl andα_(2)-Ti_(3)Al exhibit similar features as fcc and hcp metals,***,over long-term annealing where diffusion is significant,60°superdipoles inγ-TiAl are stable,whereas the stability of super-dipoles inα2-Ti3 Al increases with dipole height and orientation *** influence on mechanical properties can be well evaluated by integrating these results into mesoscale or constitutive models.

关键词： TiAl dislocation dipole Mechanical property Atomistic simulation

Microstructure change in Fe-based metallic glass and nanocrystalline alloy induced by liquid nitrogen treatment

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Journal of Materials Science & Technology 2021年第10期69卷 1-6页

作者： M.c.Ri d.W.ding y.H.Sun W.H.Wang Institute of Physics Chinese Academy of SciencesBeijing100190China Songshan Lake Materials Laboratory Dongguan523808China

The effects of acyclic liquid nitrogen(LN)treatment in a temperature range of-196℃to 50℃on the thermal and magnetic stability of Fe78Si9B13 and Fe73.5Si13.5B9Nb3cu1 glassy ribbons have been *** intrinsic heterogeneities of the metallic glasses can be activated through cryogenic thermal cycling,making irreversible structural changes after the treatment and inducing rejuvenation to the *** microstructural changes of both Fe-based metallic glass(MG)and nanocrystalline alloy induced by LN treatment were *** experimental results show that the LN treatment could effectively rejuvenate the Fe-Si-B MGs and change their thermomechanical and magnetic *** on the partially-crystallinity and well-known magnetic constants,the increase of the energy at the order of 10m J/g and magnetic domain wall movement and rotation at the order of 5-6μm and 0.5°-0.8°are found for FINEMET-type amorphous alloy after LN *** is also found that LN treatment can contribute a little stored energy to the magnetic domain wall movement and magnetic domain rotation.

关键词： Metallic glasses cryogenic thermal treatment Soft magnetic materials Rejuvenation Stored energy domain wall

Two sides of the heliopause

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Science china Earth Sciences 2011年第12期54卷 1830-1844页

作者： WHANG y. c catholic University of America

Interaction of the solar wind with the interstellar medium leads to the formation of the heliosphere and termination shock. This article addresses three aspects of the plasma and magnetic field on two sides of the heliopause：（1） The interstellar magnetic field surrounding the heliopause. In the limit of very low plasma β-ratio an analytical solution is obtained for the 3d interstellar magnetic field by means of a line dipole method. The undisturbed magnetic field in the upstream is allowed to have an arbitra.y inclination angle. The solution describes the heliosphere as having a blunt-nosed geometry on the upwind side and approaching a cylindrical geometry on the downwind side. The distortion of the magnetic field can penetrate very deep into the interstellar space. （2） Interaction of the interstellar neutral hydrogen with the global solar wind. The ionization process leads to removal of interstellar neutral hydrogen in the heliosphere： on the upwind side, 90% of hydrogen depletion occurs inside 60 AU, the hydrogen density changes rapidly inside 10 AU. A hydrogen cavity forms inside -4 AU; the cavity extends on the downwind side to form a long cavity wake. Outside the cavity and cavity wake, pickup protons are produced, they cause deceleration and heating of the solar wind. The wind speed and temperature also increase steadily with heliolatitude caused by the latitudinal increase in wind speed at the inner boundary. （3） The global geometry of the termination shock. The termination shock has been treated as having a closed geometry in previous heliosphere models. This study presents a new perspective that the global termination shock may have a bow-shaped open geometry. The termination shock forms on the upwind side because the forward motion of the supersonic solar wind is blocked at the blunt-nosed heliopause. However, the heliopause likely to be open on the downwind side; the motion of the supersonic solar wind is unobstructed for shock formation. Thus, the globa

关键词： solar wind interstellar medium magnetic fields plasmas magnetohydrodynamics (MHd)

Structural and mass transport properties of liquid ytterbium in the temperature range 1123 K–1473 K

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chinese Physics B 2023年第6期32卷 481-488页

作者： d d Satikunvar N K Bhatt B y Thakore department of Physics Sardar Patel UniversityVallabh VidyanagarGujarat 388120India department of Physics Maharaja Krishnakumarsinhji Bhavnagar UniversityBhavnagarGujarat 364001India

We have studied the structural and atomic transport properties of liquid f-shell yb in the temperature range 1123 K–1473 K. Pair interactions between atoms are derived using a local pseudopotential. The potential parameters are fitted to the phonon dispersion curve at room temperature. The local pseudopotential used in the present study is computationally more efficient with only three parameters, and it is found to be transferable to the liquid phase without changing the *** the various computed properties agree with reported theoretical and experimental findings, the adopted fitting scheme is justified. As a significant outcome of the study, we find that(i) the melting in yb is governed by the Lindemann's law,(ii)the mass transport mechanism obeys the Arrhenius law,(iii) the role of the three-particle correlation function in deriving the velocity autocorrelation function is small,(iv) the mean-square atomic displacement is more sensitive to the choice of interaction potential than the other bulk properties, and(v) liquid yb does not show liquid–liquid phase transition within the studied temperature range. Further, due to the good description of the structural and mass transport properties, we propose that yb remains divalent at reduced density.

关键词： transport properties pseudopotential single-particle dynamics ytterbium

Influence of Grain Size and Texture on the yield Asymmetry of Mg-3Al-1Zn Alloy

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Journal of Materials Science & Technology 2011年第1期27卷 29-34页

作者： S.M.yin c.H.Wang y.d.diao S.d.Wu S.X.Li Shenyang University of chemical Technology Shenyang 110142China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China

The yield asymmetry between compression and tension of magnesium alloy Mg-3Al-1Zn（AZ31） with different grain sizes and textures has been studied by tensile and compressive testing of as-cast,as-extruded and equal channel angular pressed（EcAPed） *** significant yield asymmetry（the ratio of yield strength between compression and tension σyc/σyt is ～0.44） was found in as-extruded specimens and the corresponding microstructure evolution during deformation revealed that {10 ˉ 12} tensile twinning is the underlying reason for the large yield *** texture and grain size are influential factors for large yield *** separate contributions of grain size and texture on yield asymmetry were investigated.

关键词： Magnesium alloys yield asymmetry Texture Grain size Equal channel angular pressing(EcAP)

AlTiN and AlTiON-coated hot work tool steels for tooling in steel thixoforming

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中国有色金属学会会刊：英文版 2010年第S3期20卷 1022-1028页

作者： y.BIROL d.ISLER Materials Institute Marmara Research CentreGebzeKocaeliTurkey department of Metallurgy and Materials Engineer ing Istanbul Technical UniversityIstanbulTurkey

X32crMoV33 hot work tool steel samples coated with AlTiN and AlTiON were submitted to thermal cycling under conditions that approximate thixoforming of steels and to sliding wear tests at 750 ℃,measured to be the cavity surface temperature shortly after the steel slurry is forced into the thixoforming *** and AlTiON coatings provide adequate protection against oxidation of the tool steel substrate,but fail to avoid thermal fatigue *** is attributed to the extensive softening of the substrate,the thermal expansion mismatch between the hot work tool steel and the coatings and residual compressive stresses inherited from the deposition *** impact of AlTiN and AlTiON coatings on the high temperature wear resistance,on the other hand,is *** improved wear resistance is attributed to the stable,protective surface oxide films.

关键词： thixoforming physical vapor deposition coating tooling steels thermal fatigue wear

control of dislocation density maximizing precipitation strengthening effect

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Journal of Materials Science & Technology 2022年第32期127卷 133-143页

作者： c.Xu W.J.dai y.chen Z.X.Qi G.Zheng y.d.cao J.P.Zhang c.c.Bu G.chen MIIT Key Laboratory of Advanced Metallic and Internetallic Materials Technology Engineering Research Center of Materials Behavior and DesignMinistry of EducationNanjing University of Science and TechnologyNanjing 210094China

The strength-ductility trade-off has been the most challenging problem for structural metals for *** strengthening is an ideal approach to enhance the strength without significantly sacrificing the *** nanoprecipitates have been successfully acquired by nanostructural design,but the number density of nanoprecipitates cannot be further *** attempted to enhance number density by introducing highly potent nucleation sites(e.g.,dislocations).However,there remains controversy over the influence of dislocations on the nucleation and growth of coherent nanoprecipitates with minimized nucleation ***,cu-rich nanoprecipitates in an HSLA steel,as a typical type of coherent nanoprecipitates,are *** combining analytical calculation and experiments,we show that dislocations are harmful for the formation of large numbered cu-rich nanoprecipitates in a certain density *** dislocations deprive solute atoms which decrease homogenous precipitation that cannot be compensated by the increase in heterogeneous *** such circumstance,cu-rich nanoprecipitates have smaller number density but larger size and higher fraction of incoherent structures due to rapid Ostwald *** a result,by controlling dislocation density,the yield strength is increased by 24%without obvious loss in ductility as compared with traditional solution-quench-age *** work would help to optimize composition and processing routes that fully exploit the nanoprecipitation strengthening effect.

关键词： cu-rich nanoprecipitates crystallographic defects Nucleation Structural transformation Ostwald ripening

EXTRUSION dIE cAE OF THE STEEL REINFORcEd PLASTIc PIPE

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Acta Metallurgica Sinica(English Letters) 2004年第3期17卷 303-306页

作者： W.Q.Ma H.y.Sun d.c.Kang K.d.Zhao Harbin Institute of Technology Harbin 150001 China Daqing Oilfield Postdoctoral Workstation Daqing 163453 ChinaHarbin University of Science and Technology Harbin 150080 China Daqing Oilfield Postdoctoral Workstation Daqing 163453 ChinaHarbin Institute of Technology Harbin 150001 ChinaHarbin Institute of Technology Harbin 150001 China

The steel reinforced plastic pipe is a new kind of pressure pipe. It is made up with steelwires and plastic. Because reinforced skeleton of the steel wire increase the complexityof plastic flow during the extrusion phase, the traditional design criteria of extrusiondie is not suitable. The study on extrusion die of the kind of pipe is very importantstep in produce development. Using finite element (FE) method in this paper, theflow rule of molten plastic inside the die has been predicted and a groap of optimalstructural parameters was obtained. These results are helpful for reducing the designcycle and improve the quality of the final product.

关键词： steel reinforced plastic pipe extrusion die computer aid engineering(cAE)