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Synchronous improvement of mechanical properties and stress corrosion resistance by stress-aging coupled with natural aging pre-treatment in an Al-Zn-Mg alloy with high recrystallization fraction

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Journal of Materials Science & Technology 2022年第26期121卷 40-51页

作者： d.zhang H.C.Jiang Z.J.Cui d.S.Yan Y.Y.Song L.J.Rong CAS Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Shi-Changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Shandong Key Laboratory of Advanced Aluminum Materials and Technology Binzhou 256606China

Enhancing the strength of Al-Zn-Mg alloys is critical to the weight-lightening of structural components in the application of high-speed trains and aerospace industries,while high stress corrosion cracking(SCC)susceptibility of Al-Zn-Mg alloys(especially the alloy with high recrystallization fraction)with high strength makes it difficult.In this study,the influence of tensile stress-aging coupled with natural aging pre-treatment on the mechanical properties and SCC resistance of Al-Zn-Mg alloy with high recrystallization fraction has been investigated.The results show that tensile stress-aging at 160℃can inhibit the dissolution of clusters/Guinier-Preston(GP)zones formed during long-term natural aging pre-treatment,which increases the number density of matrix precipitates(MPts),narrow the width of precipitate free zone(PFZ),and dramatically improve the mechanical properties of the experimental Al-Zn-Mg alloy.Meanwhile,the precipitation of the high density of MPts within the matrix will assume a large number of solute atoms during artificial aging,which will reduce the supplement of solute atoms to grain boundaries.As a result,the volume of anodic active grain boundary precipitates(GBPs)and the content of free solute atoms at grain boundaries are reduced,which reduces the possibility of initial nucleation and propagation of SCC crack.The coupled treatment method proposed in this study proves efficient in resolving the contradiction between the strength and SCC resistance in Al-Zn-Mg alloy.

关键词： Al-Zn-Mg alloy Natural aging Stress-aging Precipitates Stress corrosion cracking

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FORMATION OF Fe-N COMPOUNdS BY LASER NITRIdATION IN AN ATMOSPHERIC AMBIENT

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Acta Metallurgica Sinica(English Letters) 2003年第2期16卷 139-144页

作者： Y.L.Yang F.J.Sun d.zhang College of Science Northeastern UniversityShenyang 110004ChinaCollege of ScienceNortheastern UniversityShenyang 110004ChinaCollege of ScienceNortheastern UniversityShenyang 110004China

The formation of Fe-N compounds by laser nitriding in an atmospheric ambient was reported. By CW-CO2 laser irradiation on pure ferrite iron in the atmospheric ambient, Fe-N compounds (including Fe2N, .Fe3AT and Fe4N) are formed as a result of a laser-enhanced and temperature-enhanced reactions. The samples were analyzed with X-ray diffraction. It is found that the laser power density, scanning speed and nitrogen temperature are the main factors influencing the formation of Fe-N compounds. Nitrogen can be activated by pre-heating at some temperature. Nitrogen activation and sample surface melting by CW-CO2 laser greatly enhance the reaction between the sample surface and nitrogen beam. After annealing at 500℃for 3h, some Fe2N and Fe3N converted into more stable Fe4N.

关键词： laser nitriding nitride Fe-N compound

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THE INTERFACE OF TERNARY-BORIdE-BASEd HARd CLAddING MATERIAL

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Acta Metallurgica Sinica(English Letters) 2004年第1期17卷 47-50页

作者： Y.G.Wang Z.Q.Li d.zhang State Key Laboratory of Metal Matrix Composites Shanghai Jiaotong UniversityShanghai 200030 ChinaMechanical Engineering DepartmentShandong University Jinan 250061 ChinaState Key Laboratory of Metal Matrix CompositesShanghai Jiaotong UniversityShanghai 200030China

The interfacial microstructure of ternary-boride-based hard cladding material (YF-2) has been studied using scanning electron microanalyser (SEM), X-ray diffraction (XRd) and energy disperse spectroscopy (EdS). Results show that there are chemical reactions and elements diffusion in the interfacial zone, which make the interface bonding well and bonding strength ideal at the interface. The results gotten by studying of crack produced by Vickers indentation technique in the interfacial zone show that it is difficult to produce crack in the interface, the crack length in the cladding layer is longer than that to the interface, the crack which propagate to the interface stops at the interface rather than propagates along the interface. This suggests negligible residual stresses have developed because of thermal expansion mismatch. The bonding strength of the interface is 550MPa, which has been gotten by cutting test. The result gotten by analyzing the fracture surface shows that the fracture occurs at the side of cladding layer, which confirms that the bonding strength at the interface is higher than that in the cladding layer.

关键词： ternary boride cladding material interface micro structure

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STUdY ON dYNAMIC J-INTEGRAL OF MECHANICAL HETEROGENEOUS WELdEd JOINT

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Acta Metallurgica Sinica(English Letters) 2004年第6期17卷 934-939页

作者： F.Q.Tian d.Y.He X.Y.Li Y.W.Shi d.zhang InstituteofCompositeMaterials ShanghaiJiaotongUniversityShanghai200030China SchoolofMaterialsScienceandEngineering BeijingPolytechnicUniversityBeijing100022China

Welded joint is a mechanical heterogeneous body, and mechanical heterogeneity has great effect on dynamic fracture behaviour of welded joints. In the present investigation, dynamic response curve and dynamic J-integral of practical undermatched welded joint and whole base and whole weld three-point-bend (TPB) models containing longitudinal crack are com- puted. dynamic J-integral is evaluated using virtual crack extension (VCE) method and the computation is performed using MARC finite element code. Because of the effect of inertia, dynamic load response curve of computed model waves periodically. dynamic J-integral evaluated by VCE method is path independent. The effect of inertia has little influence on dynamic J-integral curve. The value of dynamic J-integral of undermatched welded joint is lower than that of whole base metal and higher than that of whole weld metal. The results establish the foundation of safety evaluation for dynamic loaded welded structures.

关键词： virtual crack extension welded joint dynamic response curve dynamic J-integral

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Two-stage double peaks ageing and its effect on stress corrosion cracking susceptibility of Al-Zn-Mg alloy

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Journal of Materials Science & Technology 2018年第7期34卷 1250-1257页

作者： Y.L.Wang H.C.Jiang Z.M.Li d.S.Yan d.zhang L.J.Rong CAS Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal Research Chinese Academy of Sciences School of Materials Science and Engineering University of Science and Technology of China

different artificial two-stage ageing behaviors and their effect on stress corrosion cracking （SCC） susceptibility of AI-Zn-Mg alloy have been investigated. The experimental results show that two hardness peaks present on the second-stage ageing-hardening curve when the first-stage ageing is dealt with comparatively lower temperature than the conventional one. The first peak is caused by dispersive and evenly distributed G.P. zones, while η ′phases and coarsened G.P. zones contribute to the second peak. Tensile strength of experimental alloy raises 9.6% （33.2 MPa） and SCC susceptibility decreases 38.9% by applying the second peak ageing regime instead of conventional T73. AI-Zn-Mg alloy obtains high strength and SCC resistance due to its finely dispersive matrix precipitates （MPts）, coarsened and discontinuous grain boundary precipitates （GBPs）, as well as the narrow precipitate free zone （PFZ） in the second peak ageing condition. 2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.

关键词： Al-Zn-Mg alloy Two-stage ageing double peaks ageing Stress corrosion cracking （SCC） susceptibility Grain boundary precipitates （GBPs）

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An approach to extracting information of residential areas from Beijing-1 image based on Gabor texture segmentation

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International Journal of digital Earth 2009年第2期2卷 186-193页

作者： J.Gong X.Yang F.Su Y.du d.zhang School of Remote Sensing and Information Engineering Wuhan UniversityWuhanChina State key Lab of Resources and Environment Information System CASBeijingChina

According to the features of high-resolution panchromatic imagery of Beijing-1 small satellite,an approach to extracting information of residential areas is proposed in this paper based on Gabor texture segmentation.The algorithm extracts the features in different directions and different scales by building the Gabor filter,uses cluster analysis of multiple features to segment the image,and performs the fusion processing based on morphological scale space.It solves the problems in image processing resulting from low contrast between remote sensing objects and background,the blurring of image edges and high noise.It has the benefits of direction selection and frequency selection with strong self-adaptive ability.Our experiments prove the effectiveness of the approach for extracting information of residential areas from Beijing-1 high-resolution imagery.

关键词： Gabor filter texture segmentation Beijing-1 small satellite image processing

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Co-Mn-Ni-O_2系材料阻温特性与频率关系的研究

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电子元件与材料 2007年第7期26卷 53-56页

作者：康雪雅王天雕 d.zhang T．W．Button 中国科学院新疆理化技术研究所新疆乌鲁木齐830011 Functional Materials Group IRC in Materials Processing School of Engineering University of Birminghan B 15 2TT UK

通过XRd、SEM分析和变温、变频条件下的lgρ-t测量,对Co-Mn-Ni-O2系热敏材料的lgρ-t特性与频率f的关系进行了研究。结果表明:CoMn1.4Ni0.6O4尖晶石型氧化物热敏电阻材料的阻温特性在0.1~1MHz和–70^+100℃,发生了PTC向NTC的转变,且转... 详细信息

通过XRd、SEM分析和变温、变频条件下的lgρ-t测量,对Co-Mn-Ni-O2系热敏材料的lgρ-t特性与频率f的关系进行了研究。结果表明:CoMn1.4Ni0.6O4尖晶石型氧化物热敏电阻材料的阻温特性在0.1~1MHz和–70^+100℃,发生了PTC向NTC的转变,且转变点的温度(–70~–10℃)和f(0.1~1MHz)与材料电阻率ρ有关。根据电导率σ和载流子浓度n、载流子迁移率μ之间的关系,用小极子跳跃导电理论对上述现象作了解释。

关键词：电子技术频率热敏电阻 NTC PTC 小板子

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工艺参数变化对冷喷涂铝沉积性能的影响

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中国表面工程 2008年第4期21卷 1-7页

作者： d.zhang P.H.Shipway d.G.McCartney 诺丁汉大学机械、材料、制造工程和管理学院先进材料组英国诺丁汉大学园NG7 2RD

在环境温度下以氦气为驱动气,在低碳钢基体上冷喷涂铝粉,采用工业纯铝粉,颗粒尺寸范围为-75+15μm。测得涂层沉积效率达到40%,孔隙率低于1.0vol%,涂层的硬度由铝粉末的硬度31kgf.mm-2提高到了53kgf.mm-2,这主要是涂层内产生严重塑性变... 详细信息

在环境温度下以氦气为驱动气,在低碳钢基体上冷喷涂铝粉,采用工业纯铝粉,颗粒尺寸范围为-75+15μm。测得涂层沉积效率达到40%,孔隙率低于1.0vol%,涂层的硬度由铝粉末的硬度31kgf.mm-2提高到了53kgf.mm-2,这主要是涂层内产生严重塑性变形的结果。研究了滞止压力、喷涂距离、送粉速率和喷枪与基板相对运动速度等工艺参数变化对沉积效率的影响。结果表明,以上每一个工艺参数的变化均对沉积效率产生显著影响。滞止压力、喷涂距离和送粉速率通过改变颗粒碰撞速度来影响沉积效率;当碰撞速率降低时沉积效率降低。然而,当颗粒速度降低时,由于参与冲击的颗粒(非沉积颗粒)比例增加,涂层的孔隙率并没有被影响。当增加喷枪与基体的相对运动速度时,沉积速率显著降低;这一结果表明沉积效率还存在某种喷射流量或剂量的影响因素,例如在沉积初期的"激活"期,喷射剂量就直接影响了沉积效率。

关键词：冷喷涂 Al涂层工艺参数沉积性能

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New type X—ray mask fabricated using inductvely coupled plasma deepetching

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Beijing Synchrotron Radiation Facility 2001年第2期 100-103,页

作者： d.Chen W.Lei S.Wang C.Li X.Guo H.Mao d.zhang F.Yi InstituteofMicroelectronics PekingUniversityBeijing100871China SynchrotronRadiationLaboratory InstituteofHihgEnergyPhysicsBeijing100039China TheStateLaboratoryofMicro／NanoFabricationTechnology Res

The fabrication of X-ray masks is a critical and challenging process in LIGA technique.As inductively coupled plasma(ICP) deepetching appears to be the most suitable source for deep silicon etching,we fabricated a new type X-ray mask using this technique.In comparison with other types of X-ray masks,the mask we fabricated has the advantages of its low cost and its simple fabrication process.Besired microstructures have also been fabricated using this new type X-ray mask in LIGA technique.

关键词：掩膜 X射线等离子体刻蚀微加工

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Population collapses in the pre-modern period:case study of the Fuping County, Northwest China

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Chinese Journal of Population,Resources and Environment 2017年第4期15卷 365-373页

作者： Jie Fei david d.zhang Institute of Chinese Historical Geography Fudan University department of Geography The University of Hong Kong

The pre-modern history of population change in the Fuping County(Shaanxi Province, China)during the Ming and Qing dynasties(Ad 1368-1911) was reconstructed using historical sources.The Fuping County experienced two major population collapses, i.e. the late Ming dynasty(1550-1640 s) and the 1860-1880 s. The first one was caused by the great Ad 1556 earthquake and the extreme droughts and warfare in the 1630-1640 s. The second one was caused by warfare and extreme droughts. As a whole, natural disasters, including extreme drought and great earthquake, were the key direct causes of population collapse, and climatic cooling would be a potential indirect cause. It is very interesting that population collapses occurred almost synchronously in the Fuping County and whole China, and the trends of population change were also very similar. Climate-population relationship in China would be valid at finer geographic level,and climatic cooling could be a potential indirect cause of population collapse.

关键词：人口变化 pre 倒塌中国案例西北自然灾难冷却能

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