Dynamic recrystallization of electroformed copper liners of shaped charges in high—strain—rate plastic deformation

The microstructures in the electroformed copper liners of shaped charges after high-strain-rate plastic deformation were in vestigated by transmission microscopy(TEM).Meanwhile,the orientation distribution of the grains in the recovered slug was examined by the electron backscattering Kikuchi pattern(EBSP) technique.EBSP analysis illustrated that unlike the as-formed electroformed copper liners of shaped charges the grain orientations in the recovered slug are distributed along randomly all the directions after undergoing heavily strain deformation at high-strain rate.Optical microscopy shows a typical recrystallization structure,and TEM examination reveals dislocation cells existed in the thin foil specimen.These results indicate that dynamic recovery and recrystallization occur during this plastic deformation process,and the associated deformation temperature is considered to be higher than 0.6 times the melting point of copper.     

Microstructure and penetration behavior of electroformed copper liners of shaped charges during explosive detonation deformation

The microstructure in the electroformed copper liners of shaped charges prepared with different electrolytes was studied by Scanning Electron Microscopy （SEM） and Electron Backscattering Kikuchi Pattern （EBSP） methods. SEM observations revealed the existence of columnar grains in electroformed copper liners of shaped charges formed by electrolyte without any additive and the average grain size is about 3 μm. When an additive is introduced to the electrolyte, the grains formed in the copper liners become equiaxed and finer. EBSP results show that the columnar grain grown during electroformation has the most preferential growth direction, whereas a micro-texture does not exit in the specimen prepared by electrolyte with the additive. Further, explosive detonation deformation experiments show that penetration depth is dramatically improved when the electroformed copper liners of shaped charges exhibit equiaxed grains.     

Microstructure evolution of single crystal copper wires in cold drawing

The deformation microstructure evolution of single crystal copper wires produced by OCC method has been studied with the help of TEM, EBSD and OM. The results show that there are a small number of dendrites and twins in the undeformed single crystal copper wires. However, it is difficult to observe these dendrites in deformed single crystal copper wires. The structure evolution of deformed single crystal copper wires during drawing process can be divided into three stages. When the true strain is lower than 0.94, macroscopic subdivision of grains is not evident, and the microscopic evolution of deformed structure is that the cells are formed and elongated in drawn direction. When the true strain is between 0.94 and 1.96, macroscopic subdivision of grains takes place, and the number of microbands located on {111} and cell blocks is much more than that with the true strain lower than 0.94. When the true strain is larger than 1.96, the macroscopic subdivision of grains becomes more evident than that with the true strain between 0.94 and 1.96, and S-bands structure and lamellar boundaries will be formed. From EBSD analysis, it is found that part of 〈100〉 texture resulting from solidifying is transformed into 〈111〉 and 〈112〉 due to shear deformation, but 〈100〉 texture component is still kept in majority. When the true strain is 0.94, the misorientation angle of dislocation boundaries resulting from deformation is lower than 14°. However, when the true strain arrives at 1.96, the misorientation angle of some boundaries will be greater than 50°, and the peak of misorientation angle distribution produced by texture evolution is located in the range between 25° and 30°. Supported by the National Natural Science Foundation of China (Grant Nos. 50471098 and 59971033), the Natural Science Foundation of Shaanxi Province, China (Grant No. 2003E101), and the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institution of MOE, China     

Mechanical properties of electroformed copper layers with gradient microstructure

The electroformed copper layer with gradient microstructure was prepared using the ultrasonic technique.The microstructure of the electroformed copper layer was observed by using an optical microscope (OM) and a scanning electron microscope (SEM).The preferred orientations of the layer were characterized by X-ray diffraction (XRD).The mechanical properties were evaluated with a Vicker's hardness tester and a tensile tester.It is found the gradient microstructure consists of two main parts:the outer part (fa...     

Characteristics and Microstructure of Graphite Encapsulated Iron Nanoparticles

The graphite encapsulatedα-Fe particles were prepared by reduction of stage-2 and stage-3 FeCl 3 graphite intercalation compounds(GICs)with metallic potassium.X-ray diffraction analysis(XRD),energy dispersive X-ray spectroscopy(EDS)investigation and transmission electron microscopy(TEM) observation show that the reduction products of stage-2 FeCl 3 -GICs contains more abundantα-Fe nanoparticles than those of stage-3.High-resolution TEM(HRTEM)observation reveals that the nanoparticle ofα-Fe was polycrystals or twins,which was real or quasi two-dimension in shape,and whose space orientation was strictly controlled by the graphene.Based on the experiment results,a possible growth model of the graphite encapsulatedα-Fe was proposed.     

三轴剪切过程中软黏土的微观结构及分形特征

土的物质组成和内部结构是决定土物理力学性质的主要因素;当土性质变化时,土中孔隙大小和形状变化最直观.为研究三轴剪切过程中软黏土微观结构变化特征,利用扫描电子显微镜获取了软黏土在不同应变速率和不同应变阶段的三轴固结不排水剪切试验后土试样的SEM图像;计算得到了软土的等效孔径和孔隙（颗粒）分维值.研究表明,该软黏土具有团粒-絮凝结构.试验前后软黏土中的孔隙均以小孔径、中孔径为主,大孔径孔隙分布较少;大孔隙主要存在于原状土和剪切破坏后土样中.剪切过程中存在一个影响孔隙分布随应变速率变化的应变阈值.软黏土具明显分形特征,孔隙分维值为1.891~1.750,颗粒分维值为1.825~1.908;在剪切过程中,颗粒分布分维值增大,孔隙分布分维值减小,孔隙大小和形状变化最显著.     

纯镍多晶体循环形变过程中位错结构的TEM研究

本文对纯镍多晶体循环形变过程中位错结构,特别是驻留滑移带(PSB)的形成及特性进行了TEM研究,并用选区电子衍射确定了晶粒膜面及其它晶体学取向。结果表明在循环饱和的开始点附近已观察到以梯状花样为特征的PSB;证明循环硬化阶段的末端基本上与PSB的成核相对应。并证实PSB结构是一种体效应。     

Synthesis and characterization of phase change memory cells

Phase change memory (PCM) cells based on Ge₂Sb₂Te₅ were synthesized and investigated. Current-voltage measurements demonstrated different final resistances. Transmission electron microscopy (TEM), high resolution electron microscopy (HREM) and the energy dispersive X-ray spectroscopy (EDS) analyses were used to characterize the microstructures of the PCM cells. The architectures, structures and defects in the cells including the deposited elemental distributions and the interfacial structures between electrodes and barrier layers were studied in detail. Supported by the National Basic Research Program of China (Grant No. 2007CB935400), Key Project of Beijing Education Committee Program (Grant No. JB102001200801) and Program for New Century Excellent Talents in University (Grant No. 05009015200701)     

基于NMR和SEM的软土微观结构特征试验研究

软土的含水特性和微观结构是决定其物理力学性质的主要因素. 以南沙软土为研究对象,运用核磁共振和扫描电子显微镜两种微观结构试验方法,获取了软土的弛豫时间T₂谱图和扫描电子显微镜图像,总结了两种软土（淤泥和淤泥质土）的水相分布和孔径分布规律. 研究表明,南沙软土的T₂分布曲线呈双峰型,土中存在两种状态的水分,第一种状态水超过质量的99%,孔隙多、孔径小,孔径分布主要集中在0.1~20 μm的区间. 南沙软土常见的微观结构类型为絮状结构、蜂窝结构和凝块结构3类. 计算了平均孔隙半径、平均孔隙面积、面孔隙率、孔隙形状因子和孔隙分维数等微观结构参数. 最后,对比分析了两种测试方法和应用中需注意的几个问题.     

银试样的电解液制备及工艺参数优化

为了有效地分析银试样的微观组织及形变织构,结合透射电镜和电子背散射衍射,制备了银试样的电解液,优化了电解抛光工艺参数.研究结果表明：利用配比为硫酸50mL＋冰乙酸115mL＋高氯酸6mL＋甲醇350mL＋草酸12g＋硫脲77g的电解液,分别在温度为0～25℃,电压为5～25V,时间为3～5min和温度为0～25℃,电压为15～20V的条件下,对试样Φ3mm×0.1mm和10mm×3mm×2mm进行电解抛光,获得了大薄区的透射电镜试样和标定率高达85%的电子背散射衍射试样.     

Microstructure and texture evolution during warm compression of the magnesium alloy AZ31

The evolution of the microstructure and texture with strain during compression at 150℃ of the magnesium alloy AZ31 has been investigated using the electron backscattered diffraction (EBSD) technique. The initial samples were chosen to have a strong basal plane texture with the crystal c-axes perpendicular to the compression direction. The EBSD data provide evidence concerning the relative activity of both {10-12} extension twinning and slip, and suggest that non-basal slip is important in samples deformed to a strain of more than 0.2. The relative contributions of the twinning and the slip during deformation have been discussed based on the results above.     

Cu-Ti合金Spinodal分解透射电镜衍射斑的计算机模拟

合金中的点阵波可看作由一系列不同波矢代表的平面波迭加而成。正是这些平面波与入射Ｘ光子的相互作用产生不同程度的散射,结果在Ｘ射线衍射主峰两侧出现边带（漫散峰或卫星峰）。引入浓度分布的矩形波波长及波形不对称因子αｙ、贫富溶质区波幅和散射因子,在倒易空间中对各衍射波波幅矢量求和,即能模拟出合金中沿某一晶向出现的调幅波波幅,最终可得衍射强度。通过改变不对称因子αｙ及贫、富溶质区的浓度差,所得几条Ｘ射线衍（ａ）电子衍射斑照片（ｂ）Ｋｕｂｏ（ｃ）Ｋｈａｃｈａｔｕｒｙａｎ（ｄ）本文模拟衍射花样图２　Ｓｐｉｎｏ…     

Microstructure and mechanical properties of automobile beam steels produced by EAF-CSP process

The microstructure, mechanical properties, and misorientation of automobile beam steels produced by EAF-CSP process were studied using optical microscopy （OM） and electron back-scattered diffraction （EBSD）. It is shown that the microstructure of strips is mainly polygonal ferrite, and the average grain size is about 5-8 μm. The electron back-scattered diffraction results show that grain boundaries in ferrite are basically high-angle grain boundaries without remarkable preferred orientation. Hot strips of automobile beam steels possess a good combination of strength and plasticity because of their fine microstructures and low quantity of impurities.     

Microstructure of aluminum/copper clad composite fabricated by casting-cold extrusion forming

An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface are refined in the radial profiles of cone-shaped deformation zone,but the grains in the center maintain the original state and the grain size is non-uniform.A clear boundary presents between the refined area and center area.In contrast,the copper grains in the radial profiles have been significa...     

Effects of External Stresses on the Carbide Precipitation in Bainite Transformation

TEM observation of carbide precipitates in bainite has been carried out for steel 40CMD8. Specimens transformed at 350℃ and 450℃ without external stress contain respectively the lower and the upper bainite. No fundamental change in carbide precipitation is observed in specimen transformed at 350℃ under stress of 128MPa. The very fine cementite is found precipitated within the upper bainite plates in specimen transformed at 450℃ under stress of 144MPa, which can be explained as the result of the difficulty of carbon diffusing out of the massive ferrite plate within a much shortened transformation time due to the external stress. For all the specimens examined, Bagaryatskii orientation relationship is found existing between the carbides and ferrite matrix.     

钠还原钽粉微观形态的观察及物理性能的调控

用扫描电镜和透射电镜观察了氟钽酸钾钠还原生产的钽粉的形貌和内部微观结构,它是一种以团聚体为基本粒子的粉末.通过生产工艺条件的调节和控制,生产出物理性能、电气性能适合于制作高性能的固体钽电解电容器的钽粉.     

Natural Mineral-marine Manganese Nodule as a Novel Catalyst for the Synthesis of Carbon Nanotubes

1 IntroductionCarbon nanotubes (CNTs) are globally in the lime-light as a newfancy material of the 21st century andtheyare broadening their applications to almost all scientificareas . Several methods , such as arc-discharge va-porization[1],laser vaporization[2],chemical vapor depo-sition (CVD)[3-4]and others[5], have been developed tofabricate CNTs (including single and multi wall) up tonow.It is very well possible that the CVD method,be-cause of its simplicity andlowcost ,will provide …