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Mechanical Behavior and Failure Mechanism of an As-Extruded Mg-11wt%Y Alloy at Elevated Temperature

Acta Metallurgica Sinica(English Letters) 2024年第6期37卷 969-981页

作者： Lan Zhang dao-kui xu Bao-Jie Wang Cui-Lan Lu Shuo Wang Xiang-Bo xu Dong-Liang Wang Xin Lv En-Hou Han School of Materials Science and Engineering University of Science and Technology of ChinaShenyang110016China Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Environmental and Chemical Engineering Shenyang Ligong UniversityShenyang110159China Key Lab of Electromagnetic Processing of Materials Ministry of EducationNortheastern UniversityShenyang110819China Institute of Corrosion Science and Technology Guangdong510070China

Through carrying out the high-temperature tensile experiments on an as-extruded Mg-11wt%Y alloy at 350℃,400℃,450℃,500℃and 550℃,the mechanical behavior and fracture mechanisms at elevated temperatures are investigated and *** results show that with the increase of temperature,the yield strength and ultimate tensile strength of the alloy increase at first and then decrease,while that the elongation ratio decreases firstly and then *** the sample being tested at 350℃,the values of yield strength,ultimate tensile strength and the elongation ratio are 188 MPa,266 MPa and 11%,*** 400℃,the yield strength and ultimate tensile strength reach the maximum values of,respectively,198 MPa and 277 MPa,but the elongation ratio is the lowest and its value is only 8%.When the applied temperature is increased to 550℃,the values of yield strength and ultimate tensile strength,respectively,decrease to 140 MPa and 192 MPa and the elongation ratio increases to 38%.Failure analysis demonstrates that the fracture surfaces of different samples are mainly composed of plastic dimples and exhibit the typical characteristic of ductile *** observation to the fracture side surfaces indicates that at the temperatures of 350℃and 400℃,microcracks mainly initiate in the interior of Mg_(24)Y_(5)*** the temperatures are 450℃,500℃and 550℃,the cracks preferentially initiate at the Mg_(24)Y_(5)/α-Mg interfaces.

关键词： Mg-Y alloy High-temperature tensile properties Fracture mechanism Failure analysis

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Effect of phosphate conversion film on fatigue and corrosion fatigue behavior of an as-rolled Mg–3.08Zn–0.83Al(in wt.%)alloy

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Journal of Iron and Steel Research(International) 2023年第12期30卷 2557-2565页

作者： Bao-jie Wang dao-kui xu Shuo Wang Xiang-bo xu En-hou Han School of Environmental and Chemical Engineering Shenyang Ligong UniversityShenyang110159LiaoningChina Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang110016LiaoningChina Binzhou Institute of Technology Binzhou256606ShandongChina Shandong Key Laboratory of Advanced Aluminium Materials and Technology Binzhou256606ShandongChina Key Lab of Electromagnetic Processing of Materials Ministry of EducationNortheastern UniversityShenyang110819LiaoningChina

Through investigating and comparing the fatigue behavior of an as-rolled Mg–3.08Zn–0.83Al(in wt.%)alloy performing surface phosphate conversion film treatment,it revealed that the determined fatigue strength of surface treated samples at 106 cycles in air was 65 MPa,whereas the fatigue strength was only 35 MPa when tested in 3.5 wt.%NaCl *** analysis demonstrated that in air,the fatigue crack initiation was mainly dominated by the interaction between the retarding effect of phosphate conversion film on cyclic slips occurring in the underneath *** the matrix cannot endure the accumulated stress concentration due to the irreversibility of cyclic slips,the fatigue crack will preferentially initiate at sample *** the phosphate conversion film cracked easily under the cyclic loading and lost its protectiveness on the substrate in 3.5 wt.%NaCl solution,fatigue cracks were preferentially nucleated at the localized corrosion pits.

关键词： Mg alloy Corrosion fatigue Surface film Pitting Crack initiation

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Analysis and Modeling of Friction Stir Processing-Based Crack Repairing in 2024 Aluminum Alloy

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Acta Metallurgica Sinica(English Letters) 2017年第3期30卷 228-237页

作者： Jun-Gang Ren Lei Wang dao-kui xu Li-Yang Xie Zhan-Chang Zhang Department of Mechanical Engineering and Automation Northeastern University Department of Electromechanical Engineering Shenyang Aerospace University Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of Sciences

Abstract A friction stir processing-based method was used to repair cracks in the 2024 aluminum alloy plates. The temperature field and plastic material flow pattern were analyzed on the basis of experimental and finite element simulation results. Microstructure and tensile properties of the repaired specimens were studied. The results showed that the entire crack repairing was a solid-phase process and plastic materials tended to flow toward the shoulder center and then resulted in the repairing of cracks. Meanwhile, the coarse grain structures were refined in repaired zone （RZ）, while the grains in thermal-mechanically affected zone and heat-affected zone were elongated and driven to grow up. Meanwhile, large phases are crushed into small particles and dispersed inside the RZ. Finally, the strength of the repaired specimens can be restored dramatically and their ductility can be partially restored. After heat treatment, the tensile properties of the repaired specimens can be further enhanced.

关键词： Friction stir processing Crack repairing Aluminum alloy Microstructure Hardness Tensile properties

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Research Progress on the Corrosion Behavior of Magnesium-Lithium-Based Alloys: A Review

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Acta Metallurgica Sinica(English Letters) 2019年第1期32卷 1-9页

作者： Bao-Jie Wang Ji-Yu Luan dao-kui xu Jie Sun Chuan-Qiang Li En-Hou Han School of Environmental and Chemical Engineering Shenyang Ligong University Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal Research Chinese Academy of Sciences Environmental Corrosion Center Institute of Metal ResearchChinese Academy of Sciences

In this review paper, the research progress on corrosion behavior of hexagonal close-packed(HCP) singular phase, body cubic-centered(BCC) singular phase and(HCP + BCC) duplex-structured Mg–Li alloys has been summarized and reviewed, and the future trend about the studies on corrosion behavior of Mg–Li-based alloys and possible solving methods for the improvement in corrosion resistance are discussed also.

关键词： Magnesium–lithium alloys Crystallographic structure Corrosion behavior Corrosion product film Corrosion mechanism

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Influence of Zn Content on Microstructure and Tensile Properties of Mg–Zn–Y–Nd Alloy

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Acta Metallurgica Sinica(English Letters) 2018年第4期31卷 351-361页

作者： Bei-Ning Du Zi-Yang Hu Li-Yuan Sheng dao-kui xu Yu-Feng Zheng Ting-Fei Xi Shenzhen Institute Peking University Shenzhen Yezhan Electronics Co. Ltd Institute of Metal Research Chinese Academy of Sciences

In the present study,the effect of Zn content on the microstructure and deformation behavior of the as-cast Mg-Zn-Y-Nd alloy has been *** results showed that as Zn content increased,the volume fraction of secondary phases ***,the phase transformation from W-phase to W-phase and I-phase *** the as-cast state,W-phase exists as eutectic and large block *** Zn content increases to 6 and 8%（wt%）,small I-phase could precipitate around W-phase ***,the effect of Zn content on the tensile properties and deformation behavior varies with the testing *** room temperature,the tensile strength increases with Zn content,whereas the elongation increases initially and then *** 250℃,as Zn content increases,the tensile strength decreases initially and then increases slightly,whereas the elongation *** 350℃,the elongation increases with Zn content,whereas the tensile strength decreases initially and then increases slightly.

关键词： Mg-Zn-Y-Nd alloy Zn content Microstructure Tensile performance

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Exfoliation corrosion of extruded Mg-Li-Ca alloy

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Journal of Materials Science & Technology 2018年第9期34卷 1550-1557页

作者： Zi-You Ding Lan-Yue Cui Rong-Chang Zeng Yan-Bin Zhao Shao-Kang Guan dao-kui xu Cun-Guo Lin College of Materials Science and Engineering Shandong University of Science and Technology Qingdao 266590 China School of Materials Science and Engineering Zhengzhou University Zhengzhou 450002 China CAS Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Science and Technology on Marine Corrosion and Protection Laboratory Qingdao 266071 China Qingdao Branch of Luoyang Ship Material Research Institute Qingdao 266101 China

Exfoliation on as-extruded Mg-1 Li-1 Ca magnesium alloy was investigated after an immersion in 3.5 wt%NaCl aqueous solution for 90, 120 and 150 days through optical microscope, digital camera, scanning electron microscope, electrochemical workstation, scanning Kalvin probe, X-ray diffraction and Fourier transform infrared spectroscope. The results demonstrated that exfoliation corrosion occurred on extruded Mg-1 Li-1 Ca alloy due to elongated microstructure parallel to surface, and delamination of lamellar structure resulted from galvanic effect and wedge effect. Skin layer with fine grains exhibited better corrosion resistance, whereas the interior with coarse grains and the intermetallic compound,Mg2 Ca particles existing in a fibrous structure, dispersed along grain boundaries and extrusion direction in a line. Furthermore, galvanic effect between Mg2 Ca particles and their neighboring a-Mg matrix facilitated dissolution of Mg2 Ca particles and a-Mg matrix; wedge effect was caused by formation of corrosion products. Exfoliation corrosion of extruded Mg-Li-Ca alloys might be a synergic effect of pitting corrosion,filiform corrosion, intergranular corrosion and stress corrosion. Finally, exfoliation corrosion mechanism was proposed.

关键词： Magnesium-lithium alloy Exfoliation corrosion Intermetallic compound Extrusion Microstructure

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Troy: Efficient Service Deployment for Windows Systems

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Chinese Journal of Electronics 2024年第1期33卷 313-322页

作者： Deyu ZHANG Yu XIE Mucong xu En CHENG Xiaoyan kui Bangwen HE Yunhao LI School of Computer Science and Engineering Central South University

The modern university computer lab and kindergarden through 12th grade classrooms require a centralized solution to efficiently manage a large number of desktops. The existing solutions either bring virtualization overhead in runtime or requires loading a large image over 30 GB leading to an unacceptable network latency. In this work, we propose Troy which takes advantage of the differencing virtual hard disk techniques in Windows *** such, Troy only loads the modifications made on one machine to all other machines. Troy consists of two modules that are responsible to generate an initial image and merge a differencing image with its parent image, respectively. Specifically, we identify the key fields in the virtual hard disk image that links the differencing image and the parent image and find the modified blocks in the differencing images that should be used to replace the blocks in the parent image. We further design a lazy copy solution to reduce the I/O burden in image merging. We have implemented Troy on bare metal machines. The evaluation results show that the performance of Troy is comparable to the native implementation in Windows, without requiring the Windows environment.

关键词： Runtime Image synthesis Merging Loading Metals Hard disks Virtualization

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Secure resource allocation against colluding eavesdropping in a user-centric cell-free massive multiple-input multiple-output system

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Frontiers of Information Technology & Electronic Engineering 2024年第4期25卷 500-512页

作者： Na LI Yuanyuan GAO kui xu Xiaochen XIA Huazhi HU Yang LI Yueyue ZHANG College of Communication Engineering Army Engineering University of PLANanjing 210007China

We investigate the resource allocation problem of a cell-free massive multiple-input multiple-output system under the condition of colluding eavesdropping by multiple passive *** address the problem of limited pilot resources,a scheme is proposed to allocate the pilot with the minimum pollution to users based on access point selection and optimize the pilot transmission power to improve the accuracy of channel *** at the secure transmission problem under a colluding eavesdropping environment by multiple passive eavesdroppers,based on the local partial zero-forcing precoding scheme,a transmission power optimization scheme is formulated to maximize the system’s minimum security spectral *** results show that the proposed scheme can effectively reduce channel estimation error and improve system security.

关键词： Cell-free Colluding eavesdropping Limited pilot resources Access point selection Security rate

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Improved nuclear mass formula with an additional term from the Fermi gas model

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Nuclear Science and Techniques 2024年第5期35卷 131-138页

作者： Xiao-Yu xu Li Deng Ai-Xi Chen Hang Yang Amir Jalili Han-kui Wang School of Science Zhejiang Sci-Tech UniversityHangzhou 310018China

Nuclear mass is a fundamental property of nuclear physics and a necessary input in nuclear *** to the complexity of atomic nuclei and nonperturbative strong interactions,conventional physical models cannot completely describe nuclear binding *** this study,the mass formula was improved by considering an additional term from the Fermi gas *** nuclear masses in the Atomic Mass Evaluation Database were reproduced with a root-mean-square deviation(RMSD)of -1.86 MeV(1.92 MeV).The new mass formula exhibits good performance in the neutron-rich nuclear *** RMSD decreases to 0.393 MeV when the ratio of the neutron number to the proton number is≥1.6.

关键词： Nuclear mass formula Neutron-rich nuclei Fermi-gas model

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Dealloying corrosion of anodic and nanometric Mg41Nd5 in solid solution-treated Mg-3Nd-1Li-0.2Zn alloy

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Journal of Materials Science & Technology 2021年第24期83卷 161-178页

作者： Gui-Jia Gao Mei-Qi Zeng En-Liang Zhang Rong-Chang Zeng Lan-Yue Cui dao-kui xu Feng-Qin Wang M.Bobby Kannan Corrosion Laboratory for Light Metals College of Materials Science and EngineeringShandong University of Science and TechnologyQingdao266590China School of Materials Science and Engineering Zhengzhou UniversityZhengzhou450002China Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Engineering University of NewcastleCallaghanNew South Wales 2308Australia

The microstructure and chemical compositions of the solid solution-treated Mg-3 Nd-1 Li-0.2 Zn alloy were characterized using optical microscope,scanning electron microscope(SEM),transmission electron microscope(TEM),electron probe micro-analyzer(EPMA)and X-ray photoelectron spectroscopy(XPS).The corrosion behaviour of the alloy was investigated via electrochemical polarization,electrochemical impedance spectroscopy(EIS),hydrogen evolution test and scanning Kelvin probe(SKP).The results showed that the microstructure of the as-extruded Mg-3 Nd-1 Li-0.2 Zn alloy containedα-Mg matrix and nanometric second phase Mg_(41)Nd_(5).The grain size of the alloy increased significantly with the increase in the heat-treatment duration,whereas the volume fraction of the second phase decreased after the solid solution *** surface film was composed of oxides(Nd_(2)O_(3),Mg O,Li_(2)O and Zn O)and carbonates(Mg CO3 and Li_(2)CO3),in addition to *** as-extruded alloy exhibited the best corrosion resistance after an initial soaking of 10 min,whereas the alloy with 4 h-solution-treatment possessed the lowest corrosion rate after a longer immersion(1 h).This can be attributed to the formation of Nd-containing oxide film on the alloys and a dense corrosion product *** dealloying corrosion of the second phase was related to the anodic Mg_(41)Nd_(5)with a more negative Volta potential relative toα-Mg *** preferential corrosion of Mg_(41)Nd_(5)is proven by in-situ observation and *** solid solution treatment of Mg-3 Nd-1 Li-0.2 Zn alloy led to a shift in corrosion type from pitting corrosion to uniform corrosion under long-term exposure.

关键词： Magnesium alloy Corrosion Second phase Rare metal Dealloying

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