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In-situ synchrotron high energy x-ray diffraction study on the internal strain evolution of D019-α2 phase during high-temperature compression and subsequent annealing in a TiAl alloy

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Journal of Materials Science & Technology 2023年第32期163卷 212-222页

作者： x.Liu L.Song A.Stark f.Pyczak T.B.zhang State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Innovation Center NPU Chongqing Northwestern Polytechnical UniversityChongqing 400000China Institute of Materials Physics Helmholtz-Zentrum HereonMax Planck-Str.1Geesthacht 21502Germany

The residual stress in the D019-α2 phase is known to be significantly higher than that in the L10-γphase in TiAl alloys after deformation due to the poor plasticity and strong mechanical anisotropy of theα2 ***,the internal stress accumulation and relaxation in theα2 phase during high-temperature deformation and annealing are scarcely *** this study,for the first time,the internal strain evolution and load partitioning between theα2 andγphases at high temperatures are characterized by in-situ synchrotron high energy x-ray diffraction(HExRD)*** plastic deformation is at least initiated at a stress of roughly 200 MPa in theγphase and 775 MPa in theα2 *** intergranular strains in theα2 phase are generated by the onset of dislocation glide in theγphase,and accentuated with the accumulated dislocations and the ensuing twinning *** unloading,great intergranular strains are preserved in theα2 phase constrained by the heavily plastically deformedγ*** subsequent heating from 400 to 1000℃,the internal strains in theα2 phase are almost fully relaxed by substantial dislocation annihilation and rearrangement in theγ*** annealing at 800℃,the internal strain relaxation is rapid in the initial 10 min,whereas considerably retarded *** extent of relaxation after holding at 800℃for 1 h is equivalent to that of heating in an effective temperature range of 680-880℃for 10 *** in-situ lattice strain measurements with various thermal relaxation schemes provide guidance for the stress relief annealing of TiAl components.

关键词： TiAl alloys Synchrotron radiation Intergranular strain Stress relaxation

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EffECT Of SILICON ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES Of YTTRIUM MODIfIED Ni_3Al BASE ALLOY IC6

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Acta Metallurgica Sinica(English Letters) 1998年第6期11卷 437-441页

作者： C.B.xiao Y.f.Han x.A.zhang Beijing Inst of Aeronautical Materials Beijing China

The effect of different amounts of silicon on the microstructure of the yttrium modified Ni3Al base alloy IC6 was studied with transmission electron microscope (TEM). The chemical compositions of phases formed due to the presence of silicon and yttrium were analyzed with energy dispersive spectrum(EDS) technique of electron probe microstructural analysis (EPMA). The results showed that a bulk shape phase rich in Mo and Si was formed in the alloys with addition of 0.10-0.20wt%Si and 0.12wt%Y, and that a needle like phase named Y-NiMo was precipitated in the interdendritic area in the alloy with addition of 0.30wt%Si and 0.12wt%Y besides the formation of the bulk shape phase mentioned above. The stress rupture properties under 1100℃/80MPa and the thermal fatigue properties at 1100℃ were improved by adding 0. 12wt%Y but decreased by adding 0.10-0.30wt%Si and 0.12wt%Y. The addition of 0. 10-0.20wt%Si and 0.12wt%Y has no obvious influence on the tensile properties of alloy IC6 at room temperature (R. T.), 760, and 900℃, respectively.

关键词： silicon yttrium Ni_3Al microstructure mechanical property

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Lightning ablation suppression of aircraft carbon/epoxy composite laminates by metal mesh

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Journal of Materials Science & Technology 2019年第11期35卷 2693-2704页

作者： f.S.Wang Y.zhang x.T.Ma Z.Wei J.f.Gao School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an710129China The Research Institute for Special Structures of Aeronautical Composite Ji’nan250023China

Three-dimensional finite element(fE)models of carbon/epoxy composite laminates with copper mesh and aluminum mesh protection were established subjected to lightning strike,in which different mesh spacing was *** of numerical method was verified and impulse current waveforms with different current peaks were applied according to aircraft lightning ***-electrical material parameters varying with temperature were added into numerical *** deletion method was used to deal with lightning ablation elements of composite *** results show that ablation area and depth of composite laminates with metal mesh protection are significantly smaller,which proves good protection effectiveness of metal meshes on anti-lightning *** denser the mesh spacing,the better the anti-lightning strike will *** of composite laminates with copper mesh has better effects than that of aluminum *** the effect of mesh spacing variation on composite structural weight and anti-lightning strike,the ideal mesh spacing was obtained.

关键词： Lightning strike Carbon/epoxy composites Ablation Mesh protection

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Towards the diffusion source cost reduction for NdfeB grain boundary diffusion process

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Journal of Materials Science & Technology 2020年第1期36卷 50-54页

作者： H.x.Zeng Z.W.Liu J.S.zhang x.f.Liao H.Y.Yu School of Materials Science and Engineering South China University of TechnologyGuangzhou 510640China

Aiming at improving the performance/cost ratio in grain boundary diffusion process(GBDP),the critical RE containing Pr-Al-Cu alloy,less expensive RE containing La-Al-Cu alloy and non-RE Al-Cu alloy were employed as the diffusion *** preliminary results show that the coercivity was successfully enhanced from 1000 kA/m to 1695,1156 and 1125 kA/m by Pr70Al20Cu10,La70Al20Cu10 and Al75Cu25(at.%) alloys diffusion,respectively,due to the formation of(Nd,Pr)-fe-B,La2 O3 and c-Nd2 O3 phases respectively,after *** is also found that the corrosion resistance can be improved by Al-Cu diffusion due to the positive effects of Al and Cu elements in grain *** present results demonstrated the various coercivity enhancement mechanisms for the GBDP based on different diffusion sources,and provided feasible solutions for cost reduction of GBDP and NdfeB production by saving RE resource.

关键词： Grain boundary diffusion Cost reduction Coercivity Microstructure Corrosion resistance

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Large deformation and wrinkling analyses of bimodular structures and membranes based on a peridynamic computational framework

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Acta Mechanica Sinica 2019年第6期35卷 1226-1240页

作者： H.Li Y.G.Zheng Y.x.zhang H.f.Ye H.W.zhang Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of ChinaChengdu 610200China International Research Center for Computational Mechanics State Key Laboratory of Structural Analysis for Industrial EquipmentDepartment of Engineering MechanicsFaculty of Vehicle Engineering and MechanicsDalian University of TechnologyDalian 116024China

In this paper,the quasi-static large deformation,wrinkling and fracture behaviors of bimodular structures and membranes are studied with an implicit bond-based peridynamic computational ***,the constant and tangential stiffness matrices of the implicit peridynamic formulations for the nonlinear problems are derived,*** former is con structed from the linearization of the bond strain on the basis of the geometric approximation while the latter is established according to the linearization of the pairwise force by using first-order Taylor’s ***,a bimodular material model in peridynamics is developed,in which the tensile or compressive behavior of the material at each point is conveniently described by the tensile or compressive states of the bonds in its ***,the bimodular material model is extended to deal with the wrinkling and fracture problems of membranes by setting the compressive micro-modulus to be *** addition,the incremental-iterative algorithm is adopted to obtain the convergent solutions of the nonlinear ***,several representative numerical examples are presented and the results demonstrate the accuracy and efficiency of the proposed method for the large deformation,wrinkling and fracture analyses of bimodular structures and membranes.

关键词： Bimodular structures Wrinkling membranes fracture problems Peridynamics Implicit numerical algorithm

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Mechanism transition of cross slip with stress and temperature in face-centered cubic metals

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Journal of Materials Science & Technology 2020年第22期54卷 159-171页

作者： K.Q.Li Z.J.zhang J.x.Yan J.B.Yang Z.f.zhang Laboratory of fatigue and fracture for Materials Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China

A/2 screw dislocation is commonly dissociated into two /6 Shockley partial dislocations on{111} planes in face-centered cubic *** the two partials are not purely screw,different mechanisms of cross-slip could take place,depending on the stacking fault energy,applied stress and tempe *** is crucial to classify the mechanisms of cross-slip because each mechanism possesses its own reaction path with a special activation *** this work,molecular dynamics simulations have been performed systematically to explore the cross-slip mechanism under different stresses and temperatures in three different metals Ag,Cu and Ni that have different stacking fault energies of 17.8,44.4 and 126.8 mJ/m^2,re *** Ag and Cu with low stacking fault energy,it is observed that the cross-slip mechanism of screw dislocations changes from the fleischer obtuse angle(fLOA),to the friedel-Escaig(fE),and then to the fL acute angle(fLAA) at low temperatures,with increasing the applied ***,when the temperature increases,the fE mechanism gradually becomes dominant,while the fLAA only occurs at the high stress *** particular,the fLOA has not been observed in Ni because of its high stacking fault energy.

关键词： Cross-slip Molecular dynamics simulation face-centered cubic metals Stacking fault energy

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HIGH-TEMPERATURE OxIDATION Of fGH96 P/M SUPERALLOY

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Acta Metallurgica Sinica(English Letters) 2007年第2期20卷 102-110页

作者： f.J. Liu M.C. zhang J.x. Dong Y. W. zhang School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083 China Central Iron and Steel Research Institute Beijing 100081 China

High temperature oxidation behaviors of fGH96 P/M superaUoy have been studied in air at temperatures ranging from 600 to 1000℃. By means of isothermal oxidation testing, x-ray diffraction, SEM （scanning electron microscopy）, and EDS （energy dispersive x-ray spectroscopy） analyses, the oxidation kinetics as well as the composition and morphology of scales were investigated. Thermodynamic calculations were used to explain the oxidation mechanism. The results showed that as the oxidation temperature increased, the oxidation rate, the scale thickness, and scale spallation increased. fGH96 P/M superalloy exhibits good oxidation resistance at temperature below 800℃. The oxidation kinetics follows an approximately parabolic rate law, and the oxide layer was mainly composed of Cr2O3 TiO2 and a little amount of NiCr2O4. The oxidation is controlled by the transmission of chromium. titanium, and oxygen through the oxide scale.

关键词： fGH96 P/M superalloy high temperature oxidation oxide scale

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fatigue Properties Improvement of Low-Carbon Alloy Axle Steel by Induction Hardening and Shot Peening:A Prospective Comparison

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Acta Metallurgica Sinica(English Letters) 2022年第8期35卷 1343-1356页

作者： G.C.Chu f.Z.Hu x.J.jin Y.zhang Q.Wang J.P.Hou Z.f.zhang Shi-Changxu Innovation Center for Advanced Material Institute of Metal ResearchChinese Academy of SciencesShenyang 110016.China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China Manshan Iron and Steel Co. Ltd.Maanshan 243000China School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Baowu Group Masteel Rail Transit Materials Technology Company Limited Maanshan 243000China

fatigue fracture is the major threat to the railway axle, which can be avoided or delayed by surface strengthening. In this study, a low-carbon alloy axle steel with two states was treated by surface induction hardening and shot peening, respectively, to reveal the mechanism of fatigue property improvement by microstructure characterization, microhardness measurement, residual stress analysis, roughness measurement, and rotary bending fatigue tests. The results indicate that both quenching and tempering treatment can effectively improve the fatigue properties of the modified axle steel. In addition, induction hardening can create an ideal hardened layer on the sample surface by phase transformation from the microstructure of ferrite and pearlite to martensite. By comparison, shot peening can modify the microstructure in surface layer by surface severe plastic deformation introducing a large number of dislocation and even cause grain refinement. Both induction hardening and shot peening create compressive residual stress into the surface layer of axle steel sample, which can effectively reduce the stress level applied to the metal surface during the rotary bending fatigue tests. On the whole, the contribution of induction hardening to the fatigue life of axle steel sample is better than that of the shot peening, and induction hardening shows obvious advantages in improving the fatigue life of axle steel.

关键词： Surface strengthening Induction hardening Shot peening Axle steel fatigue property improvement

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A review——Pitting corrosion initiation investigated by TEM

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Journal of Materials Science & Technology 2019年第7期35卷 1455-1465页

作者： B.zhang x.L.Ma Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences

Passive metals have superior resistance to general corrosion but are susceptible to pitting attack in certain aggressive media, leading to material failure with pronounced adverse economic and safety consequences. Over the past decades, the mechanism of pitting corrosion has attracted corrosion community striving to study. However, the mechanism at the pitting initiation stage is still controversy, due to the difficulty encountered in obtaining precise experimental information with enough spatial *** the accurate sites where initial dissolution occurs as well as the propagation of the dissolution by means of multi-scale characterization is key to deciphering the link between microstructure and corrosion at the atomic scale and clarifying the pitting initiation mechanism. Here, we review our recent progresses in this issue by summarizing the results in three representative materials of 316f, and Super 304H stainless steel as well as 2024-Al alloy, using in situ ex-environmental TEM technique.

关键词： Pitting initiation Dissolution TEM Inclusion Second phase

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Numerical study of convective heat transfer of a supersonic combustor with varied inlet flow conditions

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Acta Mechanica Sinica 2019年第5期35卷 943-953页

作者： W.H.fan f.Q.Zhong S.G.Ma x.Y.zhang State Key Laboratory of High Temperature Gas Dynamics Institute of MechanicsChinese Academy of SciencesBeijing 100190 China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

Characteristics of convective heat transfer of a supersonic model combustor with variable inlet flow conditions were studied by numerical simulation in this *** three-dimensional flow and wall heat flux at different air inlet Mach numbers of 2.2,2.8 and 3.2 were studied numerically with Reynolds-averaged Navier-Stokes equations with a shear-stress transport(SST)k-ωturbulence model and a three-step reaction ***,ethylene was chosen as the fuel,and the fixed fuel-to-air equivalence ratio is 0.8 in all cases in this *** results of the simulations indicate that wall heat flux distribution of the combustor is very non-uniform with several peaks of wall heat flux at varied *** the low inlet Mach number of 2.2,a shock train structure is formed in the isolator,and three peaks of wall heat flux are located respectively on the backward face of the cavity,on the side wall near the fuel injection and on the bottom wall near the injection holes,and a maximum wall heat flux reaches 5.4 MW/*** the medium inlet Mach number of 2.8,there exists a much shorter shock structure with three peaks of wall heat flux similar to that of Mach number ***,as the inlet Mach number increased to 3.2,there is no shock structure upstream of fuel injections,and the combustor flow is in a supersonic mode with different locations and values of wall heat flux *** statistical results of wall heat loading show that the change of total wall heat is not monotonic with the increase of inlet Mach number,and the maximum appears in the case of Mach number being ***,for all the cases,the bottom wall takes up more than 50%of the total heat loading.

关键词： Wall heat flux Numerical simulation Ethylene Supersonic combustor

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