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Ensemble Retrieval of Atmospheric Temperature Profiles from AIRS

Advances in Atmospheric Sciences 2014年第3期31卷 559-569页

作者： ZHANG Jie Zhenglong li Jun li jinglong li Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Key Laboratory of Meteorological Disaster of Ministry of EducationNanjing University of Information Science & Technology Cooperative Institute for Meteorological Satellite Studies University of Wisconsin-Madison

ABSTRACT Satellite-based observations provide great opportunities for improving weather forecasting. Physical retrieval of atmo spheric profiles from satellite observations is sensitive to the uncertainty of the first guess and other factors. In order to improve the accuracy of the physical retrieval, an ensemble methodology was developed with an emphasis on perturbing the first guess. In the methodology, a normal probability density function （PDF） is used to select the optimal profile from the ensemble retrievals. The ensemble retrieval algorithm contains four steps：（1） regression retrieval for original first guess; （2） perturbation of the original first guess to generate new first guesses （ensemble first guesses）; （3） using the ensemble first guesses and nonlinear iterative physical retrieval to generate ensemble physical results; and （4） the final optimal profile is selected from the ensemble physical results by using PDE Temperature eigenvectors （EVs） were used to generate the pertur- bation and generate the ensemble first guess. Compared with the regular temperature profile retrievals from the Atmospheric InfraRed Sounder （AIRS）, the ensemble retrievals RMSE of temperature profiles selected by the PDF was reduced between 150 and 320 hPa and below 400 hPa, with a maximum improvement of 0.3 K at 400 hPa. The bias was also reduced in many layers, with a maximum improvement of 0.69 K at 460 hPa. The combined optimal （CombOpt） profile and a mean optimal （MeanOpt） profile of all ensemble physical results were improved below 150 hPa. The MeanOpt profile was better than the CombOpt profile, and was regarded as the final optimal （FinOpt） profile. This study lays the foundation for improving temperature retrievals from hyper-spectral infrared radiance measurements.

关键词： ensemble retrieval perturbation eigenvectors PDF AIRS

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Effect of Submillimeter Variation in Plunge Depth on Microstructure and Mechanical Properties of FSLW 2A12 Aluminum Alloy Joints

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Acta Metallurgica Sinica(English Letters) 2020年第1期33卷 165-171页

作者： Dan Chen jinglong li Huaxia Zhao Zhejun Tan Jiangtao Xiong State Key Laboratory of Solidifi cation Processing Northwestern Polytechnical UniversityXi’an 710072China Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical UniversityXi’an 710072China AVIC Manufacture Technology Institute Beijing 100024China

Friction stir lap welding was conducted on 2 mm + 2 mm sheets of aluminum alloy 2 A12-T4. The plunge depth(PLD) was designed as 2.45–2.58 mm, which was varied in submillimeters as 2.45, 2.50, 2.53, 2.55, and 2.58 mm, and the axial force was recorded in the welding process. The results show that the PLD fluctuation in submillimeters causes significant variation in the axial force and affects the voids(i.e., Void I and Void II), hook, and effective sheet thickness(EST), among which Void I is the main factor that affects the EST. The fracture load–PLD function in the tensile shear test of the joints follows the rule of the EST–PLD function. An optimized PLD is approximately 2.55 mm, at which the EST reaches 1.71 mm, corresponding to a peak fracture load of 11.03 kN. Thus, a PLD of 2.55 mm is suggested with a tolerance of 0.02 mm, corresponding to a fracture load of 9.6–11.0 kN, i.e., within a fluctuation of 12%.

关键词： Submillimeter Plunge depth Mechanical properties Friction stir lap welding

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A New Spot Welding Technique for Fuselage

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材料导报 2019年第10期33卷 1595-1596页

作者： CHEN Dan CHAI Peng ZHAO Huaxia XIONG Jiangtao li jinglong State Key Laboratory of Solidification Processing Northwestern Polytechnical University School of Mechanical Engineering Henan University of Engineering AVIC Manufacturing Technology Institute Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical University

High strength aluminum alloys(series 2XXX and 7XXX)are kinds of precipitation-hardening alloys,which have been widely applied in manufacturing of fuselage for their high strength-to-weight ratio,good fatigue performance and damage tolerance[1-2].These structures mostly adopt lap *** traditional joining methods include riveting and bolting,which cost weight-increase and *** disadvantages could be overcome by a new joining technique—friction stir spot welding(FSSW)developed from friction stir welding(FSW).However,after wel-ding,FSSW normally leaves the workpiece with a keyhole,which decreases mechanical properties and corrosion resistance of the *** fill the keyhole,refill friction stir spot welding(RFSSW,Refill-FSSW)was invented by GKSS in *** designs a special welding tool for RFSSW,consisting of pin,sleeve and clamping ring,which are precisely assembled with indepen-dent driving systems[3].In a typical RFSSW process,the pin and sleeve move in opposite direction at a given speed ***,the speeds are set inverse proportional to their cross-sectional *** 2011,GKSS performed RFSSW on aluminum alloy and obtained the joint with good ***,RFSSW was highlighted in research,which was expected to apply in fuselage manufacturing and to replace the traditional joining methods.

关键词： High strength aluminum alloys kinds

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Microstructure and mechanical properties in the TLP joint of FeCoNiTiAl and Inconel 718 alloys using BNi2 filler

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Journal of Materials Science & Technology 2021年第2期61卷 176-185页

作者： lin Yuan Jiangtao Xiong Yajie Du Jin Ren Junmiao Shi jinglong li State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'an 710072China Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical UniversityXi'an 710072China

High entropy alloy(HEA) of Fe Co Ni Ti Al and Inconel 718 superalloy were firstly transient liquid phase(TLP) bonded by BNi2 filler due to the diffusion of Si and B in the filler to the base metals. The effects of bonding time on microstructure evolution and mechanical properties of the TLP joints were *** to the complete isothermal solidification of the joints bonded for 30 min 120 min at 1100°C,no athermally solidified zones(ASZs) formed by eutectic phases were observed in the welded zone. Thus the TLP joints were only composed by the isothermally solidified zone(ISZ) and two diffusion affected zone(DAZ) adjacent to the dissimilar base metals and the negative effect of the ASZ on joint properties can be avoided. In addition, the increase of the bonding time can also make the Ti B2 borides precipitated in the DAZ near HEA and the brittle borides or carbides in the DAZ near IN718 alloy decrease and reduce the possibility of the stress concentration happened in the joints under loading. Therefore, the highest shear strength(632.1 MPa) of the TLP joints was obtained at 1100°C for 120 min, which was higher than that of the joint bonded for 30 min, 404.2 MPa. Furthermore, the extension of the bonding time made the fracture mechanism of the joint be transformed from the intergranular fracture to the transgranular fracture. However, as the brittle borides in the DAZ near IN718 can not be eliminated completely and refining of grains also happened in such region, all the TLP joints fractured inner the DAZ near IN718 alloy.

关键词： FeCoNiTiAl alloy Inconel 718 alloy Microstructure evolution Mechanical properties Fracture mechanism

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Quasi-in-situ Observation of Interfacial Behaviours:Recrystallization and Grain Recombination during Micro-deformed Diffusion Bonding Process

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Acta Metallurgica Sinica(English Letters) 2023年第12期36卷 2031-2044页

作者： Yu Peng Shiwei li Feng Jin Yipeng Chen Wei Guo Jiangtao Xiong jinglong li State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'an 710072China Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical UniversityXi'an 710072China

The interfacial behaviours of micro-deformed diffusion bonded joints were systematically *** were two typical bonding interfacial characteristics:“bond line”and migrated grain boundaries.“Bond line”was featured as fine grains and phases on the *** critical temperature of joint characterized by“bond line”was 950℃.The increased temperature 1000℃was a critical temperature which interfacial characteristic“bond line”*** second type was characterized by interfacial migration over 1000℃,in which the bonding interfaces were composed of straight grain boundaries,triple junctions,and protruding and expanding interfacial migrated ***,two different interface migration and joint forming mechanisms were observed with elevated bonding temperature:recrystallization and grain *** first one was the discontinuous dynamic recrystallization mechanism,which was observed in the joints bonded at 950℃and 1000℃.The second mechanism was the grain boundary migration mechanism based on the grain growth mechanism,of which the typical bonding temperature was 1050℃.The joint was bonded under two kinds of grain boundary migration,including strain-induced interface grain boundary migration and interface grain boundary migration at triple junction.

关键词： Diffusion bonding Critical bonding temperature Interfacial microstructure Dynamic recrystallization Grain recombination

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Interfacial Microstructure Evolution and Mechanical Properties of TC4/MgAl_(2)O_(4)Joints Brazed with Ti-Zr-Cu-Ni Filler Metal

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Acta Metallurgica Sinica(English Letters) 2024年第12期37卷 2057-2067页

作者： Jiafen Song Wei Guo Shiming Xu Ding Hao Yajie Du Jiangtao Xiong jinglong li State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an710072China Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical UniversityXi’an710072China

In the present study,Ti-Zr-Cu-Ni amorphous filler metal was used to braze MgAl_(2)O_(4)ceramic and Ti-6Al-4V(TC4)at 875,900,925,950,975 and 1000℃for 10 *** effects of brazing temperature on interfacial microstructure and mechanical properties of the joints were *** results showed that typical microstructure of the TC4/MgAl_(2)O_(4)joint was solid solution(SS)α-Ti,acicularα-Ti+(Ti,Zr)_(2)(Ni,Cu)layer,metallic glasses and *** the increase in brazing temperature,(Ti,Zr)_(2)(Ni,Cu)layer gradually dispersed at bonding interface,a continuous layer of TiO appears near MgAl_(2)O_(4)*** the increase in brazing temperature,the hard and brittle(Ti,Zr)_(2)(Ni,Cu)layer gradually dispersed,resulting in the maximum shear strength of 39.5 *** high-resolution TEM revealed the presence of amorphous structure,which is composed of Ti,Zr,Cu,Ni and *** values ofδandΔH_(mix)are calculated to be about 8%and−39.82 kJ/mol for the amorphous phase.

关键词： Brazing TC4 titanium alloy MgAl_(2)O_(4) Microstructure High-entropy metallic glasses

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Microstructure and mechanical properties of transient liquid phase bonding DD5 single-crystal superalloy to CrCoNi-based medium-entropy alloy

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Journal of Materials Science & Technology 2022年第1期96卷 140-150页

作者： Shiwei li jinglong li Junmiao Shi Yu Peng Xuan Peng Xianjun Sun Feng Jin Jiangtao Xiong Fusheng Zhang State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical UniversityXi’an 710072China

This study focuses on the transient liquid phase(TLP)bonding of DD5 single-crystal superalloy to Cr Co Nibased medium-entropy alloy(MEA)using a BNi-2 filler *** microstructure and mechanical properties of the TLP-bonded DD5/MEA joint were evaluated,and the microstructural evolution mechanism was *** formation of the isothermal solidification zone(ISZ)depended on the diffusion of the melting-point depressants(Si and B elements)from the liquid filler into the DD5 and MEA substrates,as well as the dissolution of the *** diffused along theγchannel of DD5 and reacted to form M_(5)B_(3)boride,herein referred to as the diffusion-affected zone(DAZ I).Similarly,the Cr_(5)B_(3)boride precipitated in the Ni-rich MEA matrix adjacent to the MEA substrate(i.e.,DAZ II).Additionally,a coherent orientation of[0]_(BCY)//[011]_(FCC)and(002)_(BCY)//(200)_(FCC)was detected between M_(5)B_(3)boride with a body-centered tetragonal(BCT)structure and the face-centered cubic(FCC)*** performance of the joint was dominated by the properties of the bonding *** the bonding time increased from 20to 80 min,the athermal solidification zone(including eutectic microstructure)was gradually replaced by the ISZ exhibiting excellent plastic deformation capability,and the shear strength of the joint was *** maximum shear strength(752 MPa)was achieved when the eutectic-free joint was bonded at 1050℃ for 80 *** fracture morphology revealed a mixture mode,indicating the initiation of cracks in the DAZ II,mainly propagating in the ISZ,and passing through the DAZ I.

关键词： Microstructure Mechanical properties Transient liquid phase bonding Single-crystal superalloy Medium-entropy alloy

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Heterogeneous Deformation Behaviors of an Inertia Friction Welded Ti_(2)AlNb Joint:an In‑situ Study

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Acta Metallurgica Sinica(English Letters) 2023年第4期36卷 611-622页

作者： Dingcong Cui Qingfeng Wu Feng Jin Chenbo Xu Mingxin Wang Zhijun Wang Junjie li Feng He jinglong li Jincheng Wang State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China

A defect-free Ti_(2)AlNb joint has been obtained by the inertia friction welding(IFW)*** weld zone(WZ)is composed of B2 grains refined by discontinuous dynamic recrystallization and enhanced by grain refinement *** the average microhardness decreases by about 30 HV from the WZ to the base ***-situ SEM analysis reveals that the heterogeneous structure of the joint causes strong strain partitioning during tensile *** microcrack initiation occurs at the interface of the initial B2 phases and B2/O *** to stress concentration,the multi-slip bands and cracks tend to generate in the heat-affected zone(HAZ),causing a premature fracture.

关键词： Ti_(2)AlNb alloy Inertia friction welding Microstructure Deformation behaviors

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Simultaneous enhancement of strength and ductility in friction stir processed 2205 duplex stainless steel with a bimodal structure:experiments and crystal plasticity modeling

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Science China(Physics,Mechanics & Astronomy) 2022年第2期65卷 66-81页

作者： Yanying Hu Zexin Fang Yongbing Peng Weiqi Yang Xianfeng Ma jinglong li Yunqiang Zhao Biao Wang Sino-French Institute of Nuclear Engineering and Technology Sun Yat-Sen UniversityZhuhai 519082China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'an 710072China Guangdong Provincial Key Laboratory of Advanced Welding Technology China-Ukraine Institute of WeldingGuangdong Academy of SciencesGuangzhou 510650China

Achieving excellent strength-ductility synergy is a long-lasting research theme for structural ***,attempts to enhance strength usually induce a loss of ductility,i.e.,the strength-ductility *** the present study,the strength-ductility trade-off in duplex stainless steel(DSS)was overcome by developing a bimodal structure using friction stir processing(FSP).The ultimate tensile strength and elongation were improved by 140%and 109%,respectively,compared with those of the asreceived *** deformation and concurrent dynamic recrystallization(DRX)during FSP were responsible for the formation of bimodal *** deformation resulted in the accumulation of dislocations at the phase boundaries,which triggered interpenetrating nucleation between the austenite and ferrite phases during DRX,leading to a bimodal *** in situ mechanical responses of the bimodal structure during tensile deformation were investigated by crystal plasticity finite element modeling(CPFEM).The stress field distribution obtained from CPFEM revealed that the simultaneous enhancement of strength and ductility in a bimodal structure could be attributed to the formation of a unique dispersion-strengthened system with the austenite and ferrite *** is indicated that the present design of alternating fine austenite and coarse ferrite layers is a promising strategy for optimizing the mechanical properties of DSSs.

关键词： friction stir processing duplex stainless steel bimodal structure tensile strength crystal plasticity

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Effect of Ti-Hf-Zr-Cu-Ni high entropy alloy addition on laser beam welded joint of Ti2AlNb based intermetallic alloy

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Journal of Materials Science & Technology 2022年第25期120卷 214-226页

作者： Mirza Zahid Hussain Jiangtao Xiong jinglong li Farah Siddique lin Jie Zhang Yajie Du Xian Rong Zhou State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical UniversityXi’an 710072China State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710072China

TiAlNb based intermetallic alloys,a potential competitor for next-generation super alloys,are susceptible to high-temperature embrittlement due to nucleation of a metastable single B2 phase in the fusion zone(FZ)during laser beam welding(LBW).In this study,a high entropy alloy(HEA),Ti-Hf-Zr-Cu-Ni,was self-developed and introduced as an interlayer into laser beam welded joint(LBWJ)of Ti-22 Al-27 Nb to analyze its impact on the evolution of microstructure in the weld zone(WZ)and subsequently on joint *** examination was carried out through electron probe micro analysis(EPMA),electron backscattered diffraction(EBSD)analysis,high-resolution scanning transmission electron microscopy(HRSTEM)comprising bright field(BF),selective area electron diffraction(SAED)and high angle annular dark-field(HAADF)*** of the HEA into FZ of LBWJ triggered heterogenous nucleation during solidification,resultantly,fine-grained B2 with a greater proportion of high angle grain boundaries(HAGBs)was *** of Ti-22 Al-27 Nb LBWJ,prepared with an interlayer of HEA,was composed of planar,cellular,columnar and equiaxed dendritic grains;a solidification mode which was different from that observed in LBWJ prepared without adulteration of the *** impact of heterogenous nucleation during epitaxial solidification on mechanical properties was established through micro vickers hardness mapping and tensile test,conducted at room *** average hardness,343.5 HV,in the FZ of LBWJ prepared with an interlayer of HEA,was compatible with that of base material(BM),345 *** ultimate tensile strength(UTS),1062 MPa,and percentage elongation,11.2%,of the HEA tempered LBWJ were found in close approximation with that of BM,1060 MPa and 13.4%,respectively.A ductile mode of failure was observed during tensile test of the Ti-Hf-Zr-Cu-Ni supplemented LBWJ of Ti-22 Al-27 Nb,while quasi-cleavage mode of fracture was apparent in the joint of Ti-22 Al-27 Nb welded with

关键词： Laser beam welding Ti2Al Nb based intermetallics High entropy alloy Heterogenous nucleation

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