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Microstructures and mechanical properties of homogenization and isothermal aging Mg–Gd–Er–Zn–Zr alloy

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Rare Metals 2016年第6期35卷 443-449页

作者： Kai wen wen-bo du Ke Liu Zhao-Hui Wang Shu-bo Li College of Materials Science and Engineering Beijing University of Technology

The effects of homogenization and isothermal aging treatment on the mechanical properties of Mg-12Gd- 2Er-1Zn-0.6Zr （wt%） alloy were investigated. The precipitated long-period stacking order （LPSO） structure and the aging precipitation sequence of the conditioned alloys were observed and analyzed, respectively. The results indicate that the 14H-LPSO structure occurs after the homogenization treatment and the 131 phase forms after the isothermal aging process. These two independent processes could be controlled by the precipitation temperature range. The significant increase in the elongation of the as-cast alloy after homogenization treatment is attributed to the disappearance of the coarse primary Mgs（Gd, Er, Zn） phase and the presence of the 14H-LPSO structure. The precipitation sequence of the investigated alloy is α-Mg（SSS）/β″（D019）/β′（cbco）/β. Furthermore, the yield tensile strength （YTS） and ultimate tensile strength （UTS） values of the isothermal aging alloy have a great improvement, which could be attributed to the high density of the precipitated β′ phase.

关键词： Magnesium alloys Isothermal aging Mechanical properties Mg-Gd-Er-Zn(Zr) Microstructures

Microstructural control and hardening response of Mg–6Zn–0.5Er–0.5Ca alloy

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Rare Metals 2016年第7期35卷 526-531页

作者： Xiao-Bing Zheng Ke Liu Zhao-Hui Wang Shu-bo Li wen-bo du School of Material Science and Engineering Beijing University of Technology

The effects of heat treatment on microstructures and hardening response of Mg-6Zn4）.5Er4）.5Ca （wt%） alloy were investigated by optical microscope （OM）, scanning elec- tron microscope （SEM）, and transmission electron microscope （TEM） in this paper. The results show that the Mg（Zn4）.5Er- 0.5Ca alloy contains Mg3Zn6Erx quasicrystalline phase （I- phase） and Ca2Mg6Zn3 phase under as-cast condition. Most of the Ca2Mg6Zn3 phases and I-phases dissolve into matrix during heat treatment at 475 ℃ for 5 h. After the as-solution alloy was aged at 175 ℃ for 36 h, a large amount of MgZn2 precipitate with several nanometers precipitate. It is suggested that the trace addition of Ca results in refining the size of the precipitate, and the presence of the nanoscale MgZn2 phase is the main factor to improve the peak-aged hardness greatly to 87 HV, which in- creases about 40 % compared with that of as-cast alloy.

关键词： Mg-6Zn-0.5Er-0.5Ca alloy Heat treatment Aging hardening

Microstructure and mechanical properties of AZ31 magnesium alloy reinforced by I-phase

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Rare Metals 2019年第8期38卷 733-738页

作者： Hai-Rong Wu wen-bo du Shu-bo Li Ke Liu Zhao-Hui Wang School of Materials Science and Engineering Beijing University of Technology

The particles of Mg-Zn-Gd icosahedral quasicrystal master alloy were added into the AZ31 alloy by the repeated plastic working(RPW)process in order to improve the mechanical properties of the AZ31 alloy at room *** microstructure and tensile properties of composites were investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and tensile testing machine at room *** results suggest that the RPW process can effectively refine the matrix and make the I-phase particles distribute *** ultimate tensile strength and the yield strength of the composites reach their maximum values of 362.3 and 330.5 MPa,respectively,when the amount of I-phase particles added is10 %.Meanwhile,the elongation of the composites decreases sharply.

关键词： I-phase Reinforced composite Repeated plastic working Mechanical property

Obtaining Ultra-High Strength and ductility in a Mg–Gd–Er–Zn–Zr Alloy via Extrusion,Pre-deformation and Two-Stage Aging

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Acta Metallurgica Sinica(English Letters) 2021年第1期34卷 39-44页

作者： Lin-Yue Jia wen-bo du Jin-Long Fu Zhao-Hui Wang Ke Liu Shu-bo Li Xian du College of Materials Science and Engineering Beijing University of TechnologyBeijing 100124China

The Mg–12Gd–1Er–1Zn–0.9 Zr(wt%)alloy with ultra-high strength and ductility was developed via hot extrusion combined with pre-deformation and two-stage aging *** age-hardening behavior and microstructure evolution were ***-deformation introduced a large number of dislocations,resulting in strain hardening and higher precipitation strengthening in the subsequent two-stage *** a result,the alloy showed a superior strength–ductility balance with a yield strength of 506 MPa,an ultimate tensile strength of 549 MPa and an elongation of 8.2%at room *** finer and denserβ’precipitates significantly enhanced the strength,and the bimodal structure,smallβ-Mg5RE phase as well as denseγ’precipitates ensured the good ductility of the *** is suggested that the combination of pre-deformation and two-stage aging treatment is an eff ective method to further improve the mechanical properties of wrought Mg alloys.

关键词： Magnesium alloys Pre-deformation Two-stage aging Precipitation strengthening Mechanical properties

Microstructure and electrochemical properties of La0.8-xMMxMg0.2Ni3.1Co0.3Al0.1(x=0,0.1,0.2,0.3)alloys

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Rare Metals 2017年第8期36卷 645-650页

作者： Na Zhou wen-bo du Pei-Long Zhang Yong-Guo Zhu Zhao-Hui Wang Ke Liu Shu-bo Li College of Materials Science and Engineering Beijing University of TechnologyBeijing 100124China Whole Win Materials Science and Technology Co. LtdBeijing 100083China

The present study aims to improve electrochemical properties of the La-Mg-Ni-based hydrogen storage alloys through partial substitution for La by mischmetal（MM）.The La_（0.8-x）MM_xMg_（0.2）Ni_（3.1）Co_（0.3）Al_（0.1）（x=0,0.1,0.2,0.3）alloys were prepared by inductive melting,and their phase structures and electrochemical properties were studied by X-ray diffraction（XRD）,scanning electron microscope（SEM）,energy-dispersive X-ray spectrometry（EDX）and electrochemical *** show that the alloys mainly consist of La_2Ni_7-type phase,La_5Ni_（19）-type phase,LaNi_5-type phase and LaNi_3-type *** addition of MM does not change the phase compositions,while it leads to more uniform phase distribution and obviously promotes the formation of La_2Ni_7-type phase which possesses favorable electrochemical *** studies indicate that the substitution for La by MM could effectively improve the high rate dischargeability（HRD）of the alloy electrode,and the optimal value of HRD_（1500）（HRD at 1500 mA·g^（-1））increases from 40.63%（x=0）to 60.55%（x=0.3）.Although the activation properties of the alloy electrodes keep almost unchanged,both the maximum discharge capacity（C_（max））and the cycling stability are significantly improved by MM addition.

关键词： Hydrogen storage alloy Microstructure Discharge capacity High rate dischargeability Cyclingstability

Microstructure,mechanical properties and stretch formability of as-rolled Mg alloys with Zn and Er additions

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Rare Metals 2021年第8期40卷 2179-2187页

作者： Ke Liu Jing-Tao Liang wen-bo du Shu-bo Li Zhao-Hui Wang Zi-Jian Yu Jin-Xue Liu College of Materials Science and Engineering Beijing University of TechnologyBeijing100124China Zhengzhou Light Metal Research Institute Zhengzhou450041China

The magnesium alloy has a unique advantage in 3C fields due to its high specific strength and excellent electromagnetic shielding ***,it is difficult to deform homogeneously because of hexagonal close-packed *** the present work,the microstructure,mechanical properties and stretch formability of magnesium alloy sheets with different alloying elements were *** was indicated that a trace addition of Zn or/and Er made a key role in modifying texture,activating shear bands formation and precipitating nanoscale second phases,respectively,which resulted in an obvious improvement in both stretch formability and mechanical *** results suggested that the Mg-0.5 Zn-0.5 Er alloy sheet exhibited higher tensile strength along the rolling direction,i.e.,yield strength of 180 MPa and ultimate tensile strength of 201 MPa,accompanying with superior Erichsen value of 7.0 mm at room *** good performances of the sheet were ascribed to weakening basal texture intensity,formation of shear bands and precipitation of nanoscale W-phase(Mg_(3)Zn_(3)Er_(2)).

关键词： Mg-Zn-Er alloy Hot rolling Texture Shear band Stretch formability

Network analysis and spatial agglomeration of China’s high-speed rail: A dual network approach

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Chinese Physics B 2021年第1期30卷 612-622页

作者： Wei Wang wen-bo du Wei-Han Li Lu(Carol)Tong Jiao-E Wang School of Electronic and Information Engineering Beihang UniversityBeijing 100191China National Engineering Laboratory for Big Data Application Technologies for Comprehensive Traffic Beijing 100191China School of Cyber Science and Technology Beihang UniversityBeijing 100191China Research Institute of Frontier Science Beihang UniversityBeijing 100191China Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China

China has the largest high-speed railway(HSR) system in the world, and it has gradually reshaped the urban *** HSR system can be represented as different types of networks in terms of the nodes and various relationships(i.e.,linkages) between them. In this paper, we first introduce a general dual network model, including a physical network(PN)and a logical network(LN) to provide a comparative analysis for China’s high-speed rail network via complex network theory. The PN represents a layout of stations and rail tracks, and forms the basis for operating all trains. The LN is a network composed of the origin and destination stations of each high-speed train and the train flows between them. China’s high-speed railway(CHSR) has different topological structures and link strengths for PN in comparison with the LN. In the study, the community detection is used to analyze China’s high-speed rail networks and several communities are found to be similar to the layout of planned urban agglomerations in China. Furthermore, the hierarchies of urban agglomerations are different from each other according to the strength of inter-regional interaction and intra-regional interaction, which are respectively related to location and spatial development strategies. Moreover, a case study of the Yangtze River Delta shows that the hub stations have different resource divisions and are major contributors to the gap between train departure and arrival flows.

关键词： China’s high-speed rail dual network network analysis urban agglomeration

Hot deformation behaviors and processing maps of Mg-Zn-Er alloys based on Gleeble-1500 hot compression simulation

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Transactions of Nonferrous Metals Society of China 2016年第12期26卷 3123-3134页

作者： Cui-cui SUN Ke LIU Zhao-hui WANG Shu-bo LI Xian du wen-bo du College of Materials Science and Engineering Beijing University of Technology Beijing 100124 China

The hot deformation behaviors of as-solution Mg?xZn?yEr alloys (x/y=6, x=3.0, 4.5 and 6.0; y=0.50, 0.75 and 1.00) wereinvestigated on Gleeble?1500 thermal simulator in a temperature range of 200?450 °C at a strain rate of 0.001?1 s?1. The truestress?strain curves showed the dynamic competition between the working hardening and working softening mainly due to thedynamic recrystallization (DRX) occurring during hot compression. The constitutive equations were constructed which couldaccurately predict the peak stress of the alloys. The addition of Zn and/or Er resulted in higher deformation activation energy forMg?3Zn?0.5Er (alloy A). The processing maps were constructed as function of the temperature and the strain rate, providing theoptimum hot working conditions (i.e., at strain of 0.3, Mg?3Zn?0.5Er (alloy A): 380?430 ?C, <0.1 s?1; Mg?4.5Zn?0.75Er (alloy B):380?450 ?C, 0.01?0.1 s?1; Mg?6Zn?1Er (alloy C): 390?440 ?C, 0.01?0.1 s?1). The as-solution treated Mg?4.5Zn?0.75Er (alloy B)demonstrated more optimum hot working window comparing with Mg?3Zn?0.5Er (alloy A) and Mg?6Zn?1Er (alloy C).

关键词： Mg-Zn-Er alloy compression behavior microstructure evolution constitutive equations processing map

Microstructure and impact mechanical properties of multi-layer and multi-pass TIG welded joints of Al-Zn-Mg alloy plates

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Transactions of Nonferrous Metals Society of China 2019年第12期29卷 2496-2505页

作者： Qing-wei GAO Feng-yuan SHU Peng HE wen-bo du College of Materials Engineering Shanghai University of Engineering ScienceShanghai 201620China Shandong Provincial Key Laboratory of Special Welding Technology Harbin Institute of Technology at WeihaiWeihai 264209China State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China National Key Laboratory for Remanufacturing Beijing 100072China

The microstructure and mechanical properties of multi-layer multi-pass TIG welded joints of Al-Zn-Mg alloy plates were *** phase constituent and microstructure of different regions of the welded joints were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),transmission electron microscopy(TEM)and energy disperse spectrum(EDS),while the mechanical properties were evaluated according to the impact test.A dispersively distributed spherical and needle-likeη(MgZn2)phase was obtained in the welding *** phase composition of the heat-affected zone(HAZ)wasα(Al)+η(MgZn2)+Al6Mn,and there were a large number of dispersively precipitated nanoscale *** welded joint zone had the highest impact toughness as compared with the other parts of the *** MgZn2 phase in the weld zone contributed to the improved toughness of the ***2 MgCu phase in HAZ was proven to act as a crack source during fracture.

关键词： Al-Zn-Mg alloy thick plates multi-layer TIG welding microstructure impact mechanical property