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Microscopic stresses in carbon nanotube reinforced aluminum matrix composites determined by in-situ neutron diffraction

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journal of Materials Science & Technology 2020年第19期54卷 58-68页

作者： x.x.Zhang j.F.Zhang Z.y.Liu W.M.Gan M.Hofmann H.Andrä B.L.xiao Z.y.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China German Engineering Materials Science Centre at MLZ Helmholtz-Zentrum GeesthachtD-85747 GarchingGermany Heinz Maier-Leibnitz Zentrum(MLZ) Technische Universität MünchenD-85747 GarchingGermany Fraunhofer Institute for Industrial Mathematics Fraunhofer-Platz 1Kaiserslautern 67663Germany

One of the most desired strengthening mechanisms in the carbon nanotube reinforced aluminum matrix composites(CNT/Al)composites is the load transfer strengthening mechanism(LTSM).However,a fundamental issue concerning the LTSM is that quantitative measurements of load partitioning in these composites during loading are very *** this study,in-situ neutron diffraction study on the tensile deformation of the 3 vol.%CNT/2009 Al composite and the unreinforced 2009 Al alloy was ***{311}and{220}diffraction elastic constants(DECs)of the 2009 Al alloy were *** those DECs the average stress in the 2009 Al matrix of the composite was *** the average stress in the CNTs was separated by using the stress equilibrium *** homogenization models were also applied to explain the stress evolution in each *** results agree with experimental *** the present case,the average stress in the CNTs reaches 1630 MPa at the yield strength of the composite based on linear regression of the measured data,which leads to an increment of yield strength by about 37 *** the result of this work,an approach to quantify load partitioning in the CNTs is developed for the CNT/Al composites,which can be applied to optimize the mechanical properties of the composites.

关键词： Carbon nanotubes Aluminum matrix composites In-situ neutron diffraction Load partitioning

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SyNTHESIS AND SOLID STATE SINTERING OF W-Ni-Fe NANO-COMPOSITE POWDERS

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Acta Metallurgica Sinica(English Letters) 2000年第3期13卷 917-920页

作者： Qu, x.H. Fan, j.L. Li, y.M. Huang, B.y. Central South Univ of Technology Changsha China

The mixture of 90 wt%W, 7 wt%Ni and 3 wt%Fe elemental powders was milled in a planetary high-energy ball mill. The evolution of the structure during milling and the sintering behavior of the milled powders were tested. The results showed that by mechanical alloying W(Ni, Fe) supersaturated solid solution with nano-meter size formed, which can enhance the sintering process. Fully dense alloy from the milled powders was obtained through solid state sintering. The tensile strength of the obtained alloy is over 900 MPa which is comparable to that of the alloy sintered by traditional liquid-phase sintering from un-milled powders of the same composition.

关键词： Tungsten alloys Nickel alloys Iron alloys Mechanical alloying Powder metals Sintering Morphology Tensile strength

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IMPROVEMENT OF DISPERSION ABILITy OF NANOMETER PARTICLES By MEANS OF PLASMA POLyMERIZATION

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Acta Metallurgica Sinica(English Letters) 2002年第1期15卷 73-76页

作者： G.Q. Zhang x.G. Guo y.M. Liu y.j. Ge Beijing Institute of Printing Beijing 102600 China

In order to find a new way to improve the dispersion ability of nanometer material, an investigation on preparation of thin film with low surface energy on the surface of nanometer material by means of plasma polymerization has been done. Some physical behaviors and chemical constitution of prepared film as well as the influence of polymerized film on nanometer material were tested. All the experimental results showed that this is a possible way to improve the dispersion ability of nanometer materials.

关键词： plasma polymerization nanometer material

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Superplasticity of Ti2448 Alloy with Nanostructured Grains

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journal of Materials Science & Technology 2011年第12期27卷 1099-1104页

作者： M.j. xiao y.x. Tian G. W. Mao S.j. Li y.L. Hao R. yang School of Astronautics Northwestern Polytecllnic University Xi＇an 710072 China - Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

Ti-24Nb-4Zr-8Sn, abbreviated as Ti2448 from its chemical composition in weight percent, is a multifunctional /3 type titanium alloy with body centered cubic （bcc） crystal structure, and its highly localized plastic deformation behavior contributes significantly to grain refinement during conventional cold processing. In the paper, the nanostructured （NS） alloy with grain size less than 50 nm produced by cold rolling has been used to investigate its superplastic deformation behavior by uniaxial tensile tests at initial strain rates of 1.5 ×10-2, 1.5×10^-3 and 1.6×10-4 s-1 and temperatures of 600,650 and 700℃. The results show that, in comparison with the coarse-grained alloy with size of 50 μm, the NS alloy has better superplasticity with elongation up to ～275% and ultimate strength of 50-100 MPa. Strain rate sensitivity （m） of the NS alloy is 0.21, 0.30 and 0.29 for 600,650 and 700℃, respectively. These results demonstrate that grain refinement is a valid way to enhance the superplasticity of Ti2448 alloy.

关键词： Titanium alloy bcc crystal Superplasticity Nanostructured grain

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Composition design study of strong and ductile Mo-alloyed CoCrNi medium-entropy alloys

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材料科学技术（英文版） 2024年第19期186卷 37-47页

作者： j.x.y.n j.y.Qin j.H.Liu H.Chen y.H.Huang M.Liu C.H.xia F.Wang x.D.Cui j.B.yang Z.F.Zhang School of Materials Science and Engineering Chongqing Jiaotong UniversityChongqing 400074China Southwest Technology and Engineering Research Institute Chongqing 400039China School of Materials Science and Engineering Chongqing Jiaotong UniversityChongqing 400074China Institute of Chemical Materials China Academy of Engineering PhysicsMianyang 621900China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China

The assistance of alloying elements provides enormous opportunities for the discovery of high-performance face-centered cubic(FCC)medium-entropy alloys(MEAs).In this work,the influence of al-loying element Mo on the phase stability,stacking fault energy(SFE),deformation mechanisms,lattice distortion,and mechanical properties of(CoCrNi)100-xMox(0 ≤ x ≤ 10)MEAs was synthetically explored with the first-principles *** indicates that the FCC phase remains metastable at 0 K,and its stability degenerates with increasing Mo *** monotonous decrease of SFE is revealed with the rise of Mo content,which promotes the activation of stacking faults,deformation twinning,or martensitic *** Mo content also causes the aggravation of lattice distortion and thus triggers in-tense solid solution ***,the essential criterion for the composition design of FCC(CoCrNi)100-xMo MEAs with superior strength-ductility combination was established based on the syner-gistic effects between multiple deformation mechanisms and solid solution *** to the criterion,the optimal composition is predetermined as(CoCrNi)93Mo7 *** criterion is proved to be effective,and it can provide valuable inspiration for the development of alloying-element reinforced FCC multi-principal element alloys.

关键词： Medium-entropy alloys First-principles calculations Stacking-fault energy Solute strengthening Deformation twinning Mechanical properties

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Molecular Dynamics Simulation of Porous Layer-enhanced Dislocation Emission and Crack Propagation in Iron Crystal

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journal of Materials Science & Technology 2011年第11期27卷 1025-1028页

作者： D. Li F.y. Meng x.Q. Ma L.j. Qiao W.y. Chu Department of Physics University of Science and Technology Beijing Beijing 100083 China Corrosion and Protection Center Key Lab of Environmental Fracture （Ministry of Education） University of Science and Technology Beijing Beijing 100083 China

The internal stress induced by a porous layer or passive layer can assist the applied stress to promote dislocation emission and crack propagation, e.9. when the pipeline steel is buried in the soil containing water, resulting in stress corrosion cracking （SCC）. Molecular dynamics （MD） simulation is performed to study the process of dislocation emission and crack propagation in a slab of Fe crystal with and without a porous layer on the surface of the crack. The results show that when there is a porous layer on the surface of the crack, the tensile stress induced by the porous layer can superimpose on the external applied stress and then assist the applied stress to initiate crack tip dislocation emission under lowered stress intensity KI, or stress. To respond to the corrosion accelerated dislocation emission and motion, the crack begins to propagate under lowered stress intensity KI, resulting in SCC.

关键词： Molecular dynamics simulation Dislocation emission Crack propagation Porouslayer Stress intensity

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Coating behavior and surface hardening of Pd_(77)Cu_6Si_(17) thin film metallic glass on AZ31 magnesium alloy

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journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第12期14卷 898-905页

作者： x.H.DU y.C.CHANG H.j.PEI B.y.CHEN M.C.KUO j.C.HUANG School of Materials Sciences and Engineering Shenyang Aerospace University Department of Materials and Optoelectronic Science National Sun Yat-Sen University Department of Materials Engineering Kun Shan University

Pd77Cu6Si17(PCS) thin film metallic glasses(TFMGs) with high glass forming ability and hardness were selected as a hard coating for improving the surface hardness of AZ31 magnesium alloy. Both microindentation and nanoindentation tests were conducted on specimens with various PCS film thicknesses from 30 to 2000 nm. The apparent hardness and the relative indentation depth(β) were integrated using a quantitative model. The interaction parameters involved and relative hardness values were extracted from iterative calculations. According to the results, surface hardness can be enhanced greatly by PCS TFMGs in the shallow region, followed by gradual decrease with increasing β ratio. In addition, specimens with thinner coatings(e.g., 200nm) showed greater substrate-film interaction and those with thick coatings(e.g., 2000nm) became prone to film cracking. The optimum TFMG coating thickness in this study was estimated to be around 200 nm.

关键词： Thin film metallic glass(TFMG) Magnesium alloy Sputtering process Nanoindentation Coating thickness

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MICROSTRUCTURE AND MECHANICAL PROPERTIES OF NOVEL 718 SUPERALLOy

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Acta Metallurgica Sinica(English Letters) 2006年第6期19卷 418-424页

作者： j.H.Du x.D.Lü j.L.Qu Q.Deng j.y.Zhuang Z.y.Zhong Department of Superalloy Central Iron and Steel Research InstituteBeijing 100081China

Recently,a novel 718 superalloy with remarkable structural stability at 680℃has been designed and fabricated by CISRI(Central Iron and Steel Research Institute)*** identification of novel 718 alloy under the above-mentioned heat-treatment condition was performed using optical microscopy(OM),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).Results show that the novel 718 alloy has outstanding structural stability at 680℃.The novel 718alloy possess excellent structural stability and good mechanical properties,which is attributed to y-phase strengthening and also to the specific sandwich structure of theγ′+γ'strengthening phase.

关键词： novel 718 superalloy microstructure mechanical property stress rupture creep

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Inhibiting effect of I-phase formation on the plastic instability of the duplex structured Mg-8Li-6Zn-1.2y(in wt.%)alloy

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journal of Magnesium and Alloys 2023年第6期11卷 2196-2204页

作者： B.j.Wang D.K.xu x.Q.Zhuang L.y.Sheng School of Environmental and Chemical Engineering Shenyang Ligong UniversityShenyang110159China Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang110016China Peking University Shenzhen InstituteShenzhen Key Lab Human Tissue Regenerate&RepairShenzhen 518057China

In this work,the tensile behaviors of Mg-8%Li and Mg-8%Li-6%Zn-1.2%y alloys at ambient temperature were investigated and *** revealed that the plastic instability of Mg-8%Li alloy was quite remarkable and the variation range of serrated flowing stress can reach5 *** the Mg-8%Li-6%Zn-1.2%y alloy,the formation of I-phase(Mg_(3)Zn_(6)y)can simultaneously enhance the tensile strength and eliminate the plastic instability phenomenon,whilst its ductility was *** in-situ tensile tests revealed that for the Mg-8%Li alloy,the severity and number of slip traces present in bothα-Mg andβ-Li matrix phases increased remarkably with the applied tensile ***,slip traces were quite fine inβ-Li matrix phase and could be clearly observed when the applied tensile strain exceeded 18%.Due to the incompatibility of plastic deformation occurred in two matrix phases,the induced strain concentration atα-Mg/β-Li interfaces caused their subsequent *** the Mg-8%-6%Zn-1.2%y alloy,the I-phase distributed atα-Mg/β-Li interfaces suppressed the plastic deformation ofα-Mg matrix phase and the tensile strain was dominated by theβ-Li matrix phase,resulting in the disappearance of plastic ***,the plastic strain would preferentially concentrate at I-phase/β-Li interfaces and subsequently induced the cracking of I-phase.

关键词： Mg-li alloys Microstructure Plastic deformation Basal slip Cracking

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Plastic Effect on the Sliding Inception Bet ween a Cylinder and a Rigid Flat

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Acta Mechanica Solida Sinica 2019年第1期32卷 1-16页

作者： S.Zhang j.Huan H.Song x.Liu y.G.Wei LNM Institute of MechanicsChinese Academy of SciencesBeijing 100190China Department of Mechanical Engineering Johns Hopkins UniversityBaltimoreMD 21218USA College of Engineering Peking UniversityBeijing 100871China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

The effec ts of mat erial plasticity and local slip on the sliding inception of asperity are studied in the present ***,a semi-analytical solution is derived under the full-stick condition to analyze the effect of material plasticity on sliding ***,a friction model with contact stiffness criterion is proposed to study the cases from partial-slip condition to full-stick *** element simulations with the provided model are used to present the friction *** friction coefficient of full-s tick interface converges at a st able value,approxima tely *** saturation appears as the normalized contact interference u*is larger than 3.A transition mechanism from slip-dominated to yield-dominated takes place in the sliding *** simulation results are compared with the semi-analytical solution.

关键词： Mat erial yielding Local slip Contact stiffness criterion Finite element simulation

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