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Journal of materials Science & Technology 2022年第7期102卷 213-223页

作者： z.W.Wang J.F.zhang G.M.Xie l.H.Wu H.zhang P.Xue D.R.Ni B.l.Xiao z.Y.ma Shi-changxu Innovation Center for Advanced materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China State Key laboratory of Rolling and Automation Northeastern UniversityShenyang110819China

Ultrahigh-strength quenching and partitioning(Q&P) steels have attracted strong interests in the auto manufactory,while the comprehensive understanding in the microstructure and mechanical behavior of their welded joints is highly needed to enrich their *** the present work,it is designed to make an insight into these imperative *** strength Q&P 1180 steel joints to parent metal were successfully fabricated via friction stir welding(FSW) technique under different parameters. Apparent hardening and softening were observed in stir zone(Sz) and heat-affected zone(HAz) respectively,whose microstructures strongly depended on the peak temperature and cooling rate during *** formation of fresh martensite was the main mechanism for the Sz hardening,while the decomposition of metastable phases played key roles in the microhardness drop of the HAz.A heat source zone-isothermal phase transition layer model was proposed to clarify the impregnability of the joint strength under parameter *** dual-phase structure,nano-carbide particles,tempered initial martensite,and ultrafine-grained ferrite synergistically improved the strain hardening ability of the HAz,which eventually resulted in the equal strength FSW joints.

关键词： Ultrahigh-strength Q&P steel Friction stir welding Microstructure Mechanical property Strain hardening

A New Approach to Isothermal Precipitation Kinetics of Carbides

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Journal of materials Science & Technology 1998年第5期14卷 478-480页

作者： Fu, WT Wang, z Jing, TF zheng, Yz ma, JG Yanshan Univ Dept Mat Engn Qinhuangdao 066004 Peoples R China Harbin Frame Factory Elect Cable Harbin Peoples R China

A new approach to isothermal precipitation kinetics of carbides in undercooled austenite has been proposed firstly, which is based on measuring the changes of M-s paint vs holding time at a certain temperature. The isothermal precipitation kinetics (PTT) curve of carbides was obtained by the use of the method for 13Cr-8Mn-0.07N stainless steel, and compared with the results of chemical phase analysis and TEM method. The results show that the new method is more sensitive and convenient than the other methods.

关键词： Stainless steel

Time-inconsistent stochastic linear-quadratic control problem with indefinite control weight costs

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Science China mathematics 2024年第1期67卷 211-236页

作者： Qi lü Bowen ma School of mathematics Sichuan UniversityChengdu 610064China

A time-inconsistent linear-quadratic optimal control problem for stochastic differential equations is *** introduce conditions where the control cost weighting matrix is possibly *** such conditions,we obtain a family of closed-loop equilibrium strategies via multi-person differential *** result extends Yong’s work(2017) in the case of stochastic differential equations,where a unique closed-loop equilibrium strategy can be derived under standard conditions(namely,the control cost weighting matrix is uniformly positive definite,and the other weighting coefficients are positive semidefinite).

关键词： linear-quadratic optimal control problem time-inconsistent cost functional generalized Riccati equation indefinite control weight cost closed-loop equilibrium strategy

RANDOM-FUzzY SAFETY ANAlYSIS FOR AN AERO ENGINE TURBINE DISK

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Acta Metallurgica Sinica(English letters) 2004年第4期17卷 509-513页

作者： z.z.lü C.l.liu Y.l.Xu z.F.Yue School of Aviation Northwestern Polytechnical University Xi'an 710072 ChinaSchool of Aviation Northwestern Polytechnical University Xi'an 710072 ChinaChina Aviation Research Institute 608 Zhuzhou 412002 ChinaSchool of Mechanics Civil Engineering and Architecture Northwestern Polytechnic University Xi'an 710072 China

A numerical simulation method is presented for the random-fuzzy safety analysis of an aero engine disk. Based on the equivalent transformation from a fuzzy variable to a random variable, the equivalent random Probability Density Functions(PDFs) are got from their corresponding Fuzzy Possibility Distributions(FPDs) for the fuzzy variables. In that case the perfect numerical simulation method for the random uncertainty is employed to solve the fuzzy uncertainty. For the complex structure such as the aero engine disk with implicit relationship between the input basic variable and the response variable, the equivalent PDFs of the input basic variables are delivered simultaneously to the response variable by an empirical PDF, which is simulated by Finite Element Method(FEM). Then, in view of the fuzzy application requirement occurring in engineering usually, the reliability definition and calculation are discussed for the aero engine disk with multiple fuzzy failure modes. On the other hand, through the inverse transformation of the fuzzy variable to the random variable, the FPDs of the response variables can be calculated from their empirical PDFs as well.

关键词： random fuzzy turbine disk reliability

NUMERICAl SIMUlATION OF TEMPERATURE FIElDS IN ElECTROSlAG REMElTING SlAB INGOTS

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Acta Metallurgica Sinica(English letters) 2008年第4期21卷 253-259页

作者： l.z. Chang B.z. li Department of Metallurgical Technology Central Iron ＆ Steel Research Institute Beijing 100081 China

The method based on transient heat transfer model is adopted to simulate electro-slag remelting process. The calculated results of the model show that the process is in the quasi-steady state, and the shape of pool remains unchanged when the height of ingot is approximately 2.5-3 times the thickness of slab ingot. The change in the shape of pool is found to be strongly dependent on the pattern of melting rate, and hence, the power input; the depth of the molten pool increases with the increase in melting speed. It is concluded that a transient heat transfer model has to be used to obtain reliable input information for the entire, operatina time.

关键词： ESR Slab ingot mathematical model Shape of molten metal pool

Microstructural Evolution and Mechanical Behavior of Friction-Stir-Welded DP1180 Advanced Ultrahigh Strength Steel

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Acta Metallurgica Sinica(English letters) 2020年第1期33卷 58-66页

作者： z.W.Wang G.M.Xie D.Wang H.zhang D.R.Ni P.Xue B.l.Xiao z.Y.ma Shenyang National laboratory for materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China State Key laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China

Friction stir lap welding of a DP1180 advanced ultrahigh strength steel was successfully carried out by using three welding tools with different pin lengths. The effects of the welding heat input and material flow on the microstructure evolution of the joints were analyzed in detail. The relationship between pin length and mechanical properties of lap joints was studied. The results showed that the peak temperatures of all joints exceeded A c3, and martensite phases with similar morphologies were formed in the stir zones. These martensite retained good toughness due to the self-tempering effect. The formation of ferrite and tempered martensite was the main reason for the hardness reduction in heat-affected zone. The mechanical properties of the lap joints were determined by loading mode, features of lap interface and the joint defects. When the stir pin was inserted into the lower sheet with a depth of 0.4 mm, the lap joint exhibited the maximum tensile strength of 12.4 kN.

关键词： Advanced ultrahigh strength steel Friction stir welding Microstructure Mechanical behavior

^(199)Sn AND ^(57)Fe MOSSBAUER SPECTROSCOPIC STUDY OF THE MECHANICAllY AllOYED Fe-Sn AllOYS

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Acta Metallurgica Sinica(English letters) 1998年第5期11卷 335-341页

作者： Y.z.Yang Y.l.zhu Q.S.li X.M.ma Y.D.Dong Y.z.Chuang Guangdong Univ of Technology Guangzhou China

Nanocrystalline supersaturated solid solutions (Sa in Fe) with Sn content less than 50 at. %,and FeSn2 and Fe1.3Sn intermetallic compounds have been prepared by mechanical alloying of Fe and Sn mixture powders with composition of Fe1-xSnx (x≤0.5).The atomic alloying the formation and microstructure, especially the coordination environments, of the resultant alloys have been studied by X-ray diffraction, 57Fe and 119Sn Mossbauer Spectroscopy and diffrrential scanning calorimetry. The Fe and Sn coordination environments and the composition dependence of the hyperfine parameters on the Fe and Sn content have been fully discussed with respect to the solid dissolution alloying, grain refinement, and distortion caused or induced by mechanical alloying.

关键词： mechanical alloying Mossbauer effect nanocrystalline Fe-Sn alloy

Monotone Chains in Modulus of Two Classes of Dirichlet Coefficients

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Acta mathematica Sinica,English Series 2023年第6期39卷 1101-1114页

作者： Guang Shi lü Qiang ma School of mathematics Shandong UniversityJi'nan 250100P.R.China

let f1,...,fkand g1,...,qkbe non-CM newforms of square-free *** byλ_(sym)jf_(i)(n)the coefficients of the Dirichlet expansion of l(sym^(j)f_(i),s)andν1,...,νkthe distinct positive integers such thatλ_(sym)jf_(i)(νi)≠*** this paper,we obtain that there exist infinitely many positive integers m such that 0let expansion of l(sym^(j1)f×sym^(j2)g,s),we have a similar result.

关键词： Dirichlet coefficients Sato-Tate conjecture

Fabrication of large-bulk ultrafine grained 6061 aluminum alloy by rolling and low-heat-input friction stir welding

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Journal of materials Science & Technology 2018年第1期34卷 112-118页

作者： C.Y.liu B.Qu P.Xue z.Y.ma K.luo M.z.ma R.P.liu Shenyang National laboratory for materials Science Institute of Metal Research Chinese Academy of Sciences Key laboratory of New Processing Technology for Nonferrous Metal & materials Ministry of Education Guilin University of Technology Guangxi Key laboratory of Universities for Clean Metallurgy and Comprehensive Utilization of Nonferrous Metal Resources Guilin University of Technology State Key laboratory of Metastable materials Science and Technology Yanshan University

In this study, the ultrafine grained （UFG） 6061 Al alloys fabricated by cold rolling were friction stir welded （FSW） with different rotation rates under both air cooling and rapid cooling in water. low-heat-input parameters of 400 rpm rotation rate in water （400-Water） could effectively inhibit the coarsening of recrystallized grains, reduce the precipitation rate, and retain more dislocations of the UFG 6061 Al parent metal. 400-Water joint showed high lowest-hardness value, narrow low-hardness zone, and high tensile strength, attributing to the effect of dislocation, grain boundary, solid-solution, and precipitation hardening. This work provides an effective strategy to fabricate large-sized bulk UFG AI alloy by cold rolling with large deformation and low-heat-input FSW.

关键词： Aluminum alloys Ultrafine grained materia Friction stir welding Mechanical properties

Achieving ultra-high strength friction stir welded joints of high nitrogen stainless steel by forced water cooling

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Journal of materials Science & Technology 2018年第11期34卷 2183-2188页

作者： H.zhang D.Wang P.Xue l.H.Wu D.R.N B.l.Xiao z.Y.ma Shenyang National laboratory for materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China University of Chinese Academy of Sciences 19 Yuquan RoadBeijing 100049China

The microstructure and properties of water-cooled and air-cooled friction stir welded（FSW） ultra-high strength high nitrogen stainless steel joints were comparatively studied. With additional rapid cooling by flowing water, the peak temperature and duration at elevated temperature during FSW were significantly reduced. Compared to those in the air-cooled joint, nugget zone with finer grains（900 nm） and heat affected zone with higher dislocation density were successfully obtained in the water-cooled joint,leading to significantly improved mechanical properties. The wear of the welding tool was significantly reduced with water cooling, resulting in better corrosion resistance during the immersion corrosion test.

关键词： Friction stir welding Stainless steels Mechanical properties Corrosion