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Effects of welding parameters and post-heat treatment on mechanical properties of friction stir welded AA2195-T8 Al-Li alloy

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journal of Materials Science & Technology 2018年第1期34卷 219-227页

作者： j. Zhang X.S. Feng j.S. Gao H. Huang Z.q. Ma L.j. Guo Technical Center Shanghai Aerospace Equipments Manufacturer Shanghai 200245. China

In this study, the effects of main welding parameters （rotation speed （ω） and welding speed （υ）） on the microstructure, micro-hardness distribution and tensile properties of friction stir welded （FSW） 2195-T8 Al-Li alloy were investigated. The effects of T6 post-treatments at different solution and aging conditions on the mechanical properties and microstructure characteristics of the FSW joints were also investigated. The results show that with increasing to and v, both strength and elongation of the joints increase first, and then decrease with further increase of ω and υ. All the joints under varied welding parameters show significant strength loss, and the strength reaches only 65% of the base metal, The effect of T6 post-heat treatment on the mechanical properties of the joints depends on the solution and aging conditions. Two heat treatment processes （480 ℃×0.5 h quenching＋ 180 ℃× 12 h, 520 ℃× 0.5 h quenching＋ 180 ℃×12h aging） are found to increase the joint strength. Furthermore, low temperature quenching （480℃） is more beneficial to the joint strength. The joint strength can reach 85% of the base metal. Whereas both low temperature aging （140 ℃× 56h） and stepped aging （ 100 ℃× 12 h ＋ 180 ℃× 3 h） processes decrease the joint strength. After heat treatment all the joints show decreased ductility due to the obvious grain coarsening in the nugget zone （NZ） and thermo-mechanically affected zone （TMAZ）.

关键词： 2195-T8 Al-Li alloy Friction stir welding Welding parameters Post-heat treatment

A NEURAL NETWORK FOR WELD PENETRATION CONTROL IN GAS TUNGSTEN ARC WELDING

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Acta Metallurgica Sinica(English Letters) 2006年第1期19卷 27-33页

作者： C.S. Wu j. q. Gao Y.H. Zhao Institute of Materials joining Shandong University Jinan 250061 China

Realizing of weld penetration control in gas tungsten arc welding requires establishment of a model describing the relationship between the front-side geometrical parameters of weld pool and the back-side weld width with sufficient accuracy. A neural network model is developed to attain this aim. Welding experiments are conducted to obtain the training data set （including 973 groups of geometrical parameters of the weld pool and back-side weld width） and the verifying data set （108 groups）. Two data sets are used for training and verifying the neural network, respectively. The testing results show that the model has sufficient accuracy and can meet the requirements of weld penetration control.

关键词： neural network weld penetration control back-side weld width,gas tungsten arc welding

First-Principles Study of Phase Stability and Mechanical Property of Co_3(Al,W) Precipitates with Different Ratio of Al to W in Co Base Alloys

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稀有金属材料与工程 2009年第A3期38卷 1-4页

作者： Yao q Su X M Yan Y Zhao L W Sun j Shanghai jiaotong University Shanghai 200240 China

The energetics, electronic structure and mechanical property of Co3(Al,W) precipitates with different ratio of Al to W in Co base alloys were investigated by the method of supercell and augmented plane waves plus local orbitals within generalized gradient approximation. The calculated results show that the L12 Co3(Al,W) precipitate is the most stable when the ratio of Al to W is equal to 1. When the content of W is higher than 18.5 at%, the L12 and hexagonal structures co-exist in Co3(Al,W) precipitates at 1173 K. It is also shown that the L12 ordered Co3(Al,W) precipitates have an obvious strengthening effect in the disordered fcc cobalt matrix.

关键词：铝电子结构力学性能碳酸

Nonconforming FEMs for the p-Laplace Problem

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Advances in Applied Mathematics and Mechanics 2018年第6期10卷 1365-1383页

作者： D.j.Liu A.q.Li Z.R.Chen Department of Mathematics Shanghai UniversityShanghai 200444China

The p-Laplace problems in topology optimization eventually lead to a degenerate convex minimization problem E(v):=∫_(Ω)W(■v)dx-∫_(Ω)fvdx for v∈W_(0)^(1,p)(Ω)with unique minimizer u and stress s:=DW(ru).This paper proposes the discrete Raviart-Thomas mixed finite element method(dRT-MFEM)and establishes its equivalence with the Crouzeix-Raviart nonconforming finite element method(CR-NCFEM).The sharper quasi-norm a priori and a posteriori error estimates of this two methods are *** experiments are provided to verify the analysis.

关键词： Adaptive finite element methods nonconforming p-Laplace problem dual energy

Hardness-thermal stability synergy in nanograined Ni and Ni alloys:Superposition of nanotwin and low-energy columnar boundary

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journal of Materials Science & Technology 2023年第6期137卷 123-131页

作者： F.H.Duan Y.Lin q.Li j.H.Luan j.Lu j.Pan Y.Li Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Laboratory of Nanomaterials&Nanomechanics Department of Mechanical EngineeringCity University of Hong KongHong KongChina State Key Laboratory of Material Processing and Die&Mould Technology and School of Materials Science and Engineering Huazhong University of Science and TechnologyWuhan 430074China Department of Materials Science and Engineering City University of Hong KongHong KongChina Centre for Advanced Structural Materials Greater Bay Joint DivisionShenyang National Laboratory for Materials ScienceCity University of Hong Kong Shenzhen Research InstituteShenzhen 518057China City U-Shenzhen Futian Research Institute Shenzhen 518045China

Refining grains into nanoscale can significantly strengthen and harden metallic materials;however,nanograined metals generally exhibit low thermal stability,hindering their practical *** this work,we exploit the superposition of the contribution of nanotwins,low-angle grain boundaries,and microalloying to tailor superior combinations of high hardness and good thermal stability in Ni and Ni *** the nanotwinned Ni having a twin thickness of∼2.9 nm and grain size of 28 nm,it exhibits a hardness over 8.0 GPa and an onset coarsening temperature of 623 K,both of which are well above those of nanograined ***/Mo microalloying can further improve the onset coarsening temperature to 773 K without comprising *** analyses reveal that high hardness is achieved via strengthen-ing offered by extremely fine ***,the superior thermal stability is mainly ascribed to the low driving force for grain growth induced by the low-angle columnar boundary architecture and to the additional pinning effect on the migration of twin/columnar boundaries provided by minor Re/Mo *** present work not only reveals a family of nanotwinned metals possessing the combination of ultra-high hardness and high thermal stability but also provides a strategy for tailoring properties of metallic materials by pairing low-angle grain boundaries and twin boundaries.

关键词： Nanotwin Thermal stability Hardness Low-angle grain boundary Microalloying

Combustion Reactivity of Rice Husk: An Experimental and Numerical Investigation

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journal of Thermal Science 1993年第2期2卷 152-156页

作者： q.T.Pham I.R.Brown j.C.jones School of Chemical Engineering and Industrial Chemistry University of New South Wales Australia

The combustion reactivity of rice husk from New South Wales, Australia was measured by heating cubical baskets in controlled environment and monitoring the centre temperature. Frank-Kamenetskii's ignition theory was used to calculate the activation energy. Results agreed well with tests on other cellulosic materials, Numerical simulations of temperature changes were carried out, using a special technique to deal with non-linearities in the heat conduction equation. The numerical results indicate that the time factor should be taken into account when evaluating self-combustion risks.

关键词： combustion reactivity kinetics rice husk heat conduction numerical method.

TOTAL ENERGIES AND ELECTRONIC STRUCTURES OF CO_3Ti AND HYDROGENIZED Co_3Ti

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Acta Metallurgica Sinica(English Letters) 1998年第3期11卷 197-201页

作者： S.q.Duan S.j.Liu B.K.Ma Beijing Normal Univ Beijing China

Electronic structure calculations using the tighting-binding linear muffin-tin orbital (TB-LMTO) method have been performed for Co3Ti and its hydride CO3Ti. The computed values of lattice constants and bulk moduli agree with the experiment values. The theoritical excess enerpy and lattice staid due to hydrogen absorption consequently obtained hem the ab initio results indicate that H has the tendency to stay in Co3Ti and the ionicities of Co atomic spheres due to hydmpen absorption change from the canons to the ations. On the other hand, the changes of band structures due to hydrogenation are found to be remarkable.

关键词： total enerpy electronic structure hydrogenized Co3Ti

Analysis of local crystallographic orientation in an annealed Ti60 billet

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journal of Materials Science & Technology 2019年第4期35卷 591-595页

作者： Z.B.Zhao Z.Liu q.j.Wang j.R.Liu R.Yang Institute of Metal Research Chinese Academy of Sciences School of Materials Science and Engineering University of Science and Technology of China

A heterogeneous microstructure in terms of local orientation distribution is often found in near-α titanium alloys. The presence of large regions with similar crystallographic orientation, called ‘macrozones',could drastically decrease the fatigue performance of titanium alloys. The present work reports on the crystallographic orientation of a near-α titanium alloy, Ti60, billet after annealing in an α+β phase *** texture was found to be weak, and no obvious macrozone was found in our measured zone where the variant selection is suppressed. Meanwhile, in-depth electron backscattered diffraction(EBSD) analysis was applied to evaluate the final microstructure, and the mechanisms by which they formed were analyzed.

关键词： Titanium alloys Microstructure Texture Heat treatment EBSD

RESEARCH ON HOT FORMING PROCESS OF A RETAINING RING OF HIGH-NITROGEN STEEL

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Acta Metallurgica Sinica(English Letters) 2004年第5期17卷 767-770页

作者： H.q.Chen j.S.Liu H.G.Guo DepartmentofMaterialScienceandEngineering TaiyuanHeavyMachineryInstituteTaiyuan030024China

Mn18Cr18N, the high-nitrogen steel, is the 2nd generation material for manufacturing the retaining ring of firepower generators. In this paper, the hot deformation behavior of the material was investigated by thermo-mechanical modeling tests. And the flow stress curves of the steel were obtained for various combinations of the temperature and strain rate. Based on the results of the tests, the complex forming process of a retaining ring including punching, expanding and extrusion with an enclosure was put forward and simulated by means of numerical simulation method. The results indicate that the process is a novel and force-saved practical technology for manufacturing heavy retaining rings.

关键词： Mn18Cr18N high-nitrogen steel a retaining ring the punching with an enclosure process expanding-extrusion complex forming