Plastic Deformation of Nano-TiO_2 Ceramics Prepared by Different Methods

The comparative study of the tensile plastic deformation of nano(n)-TiO2 ceramic prepared byphysical gas condensation (P) and chemical hydrolysis precipitation (C) methods was conductedby a gas pressure forming technique at 750~800℃. The results show that n-TiO2 (P) possessesexcellent property of tensile pIastic deformation comparing with n-TiO2(C). The reason for thisis attributed to the surface cleanness and soft agglomeration of n-TiO2 (P) particfe prepared inreIatively cIean vacuum condition.

Deformation Behavior and Formability of Gradient Nano-grained AISI 304 Stainless Steel Processed by Ultrasonic Impact Treatment

The deformation behavior and formability of gradient nano-grained（GNG） AISI 304 stainless steel in uniaxial and biaxial states were investigated by means of tensile test and small punch test（SPT）. The GNG top layer was fabricated on coarse grains（CG） AISI 304 by ultrasonic impact treatment. The results showed that the CG substrate could effectively suppress the strain localization of NC in GNG layer, and an approximate linear relationship existed between the thickness of substrate（h） and uniform true strain before necking（ε_（unif））. Grain growth of NC was observed at the stress state with high Stress triaxiality T, which led to better ductility of GNG/CG 304 in SPT, as well as similar true strain after the onset of necking（ε_（neck）） compared with coarse 304 in tensile test. Ei-values of GNG/CG 304 with different structures were nearly the same at different punch speeds, and good formability of GNG/CG 304 was demonstrated. However, punch speed and microstructure needed to be optimized to avoid much lost of membrane strain region in biaxial stress state.

Measurement of the Energy Absorbed during Nanoscale Deformation of Human Peritubular and Intertubular Dentin

Mineralized tissues are usually constructed of nanosized materials with ordered hierarchical structures. The main reason for their high load-bearing ability is the multi-scale hierarchy. It is important to have a method for measuring the energy absorbed during the nanoscale deformation of mineralized tissues. The objective of this study was to use a combination of nanoindentation and elastic-plastic mechanics techniques to measure the damage resistance of peritubular and intertubular dentin, based on the energy consumed in the plastic deformation regime and the volume created by the indents. The control materials were soda-lime glass, gold, and poly-methyl methacrylate (PMMA). Plastic deformation energy was calculated from the plastic part of load-displacement curves. The mean values of peritubular dentin and intertubular dentin were 3.8 × 109, and 5.2 × 109 J/m3, respectively, compared to glass, PMMA, and gold which were 3.3 × 107, 1.3 × 109, and 3.1 × 109 J/m3, respectively. This method can be applied to study the resistance of mineralized tissues or organic/inorganic hybrid materials to deformation at the nanoscale.

Effect of tension deformation on microstructure and mechanism of electrodeposited nickel coating

Nickel coating deposits with better ductility on a lower carbon steel sheet were produced by electrodeposition method and the electrodeposited nickel coating was deformed with the strain of 10%. Then the surface morphology,the deformation texture and the mechanical properties were analyzed by scanning electron microscopy(SEM),X-ray diffractometry(XRD) and nano-indentation measurement,respectively. The principle of nano-indentation to measure the hardness and elastic modulus of nickel coating was introduced. The relation curves of the load and displacement were obtained,including the original electrodeposited samples and the samples under tension. The results show that:1) there are only two main texture components Ni(111) and Ni(200) in the nickel coating,and no new texture component is found due to the elongation;2) after tensile deformation in the coating,the surface roughness increases and the microcrack is found;3) The hardness and the elastic modulus decrease after tensile deformation;and 4) for the original electrodeposited sample,the indentation depths change with the load,the hardness and the elastic modulus decrease with the increase of the depth. In addition,the investigation of creep shows that the value of creep increases when the tensile strain ε>10%.

Effect of nano TiN/Ti refiner on as-cast and hot-working microstructure of commercial purity aluminum

A novel type nano TiN/Ti composite grain refiner （TiN/Ti refiner） was prepared by high energy ball milling, and its effect on as-cast and hot-working microstructure of commercial purity aluminum （pure Al） was investigated. The results show that TiN/Ti refiner exhibits excellent grain refining performances on pure Al. With an addition of 0.2% TiN/Ti refiner, the average grain size of pure Al decreases to 82 μm, which is smaller than that of pure Ti and Al 5Ti 1B master alloy as refiners. The microstructure of weld joint of pure Al with 0.1% TiN/Ti refiner is fine equiaxed grains and the hardness of weld joint is higher than that of the base metal. For pure Al with 40% cold deformation and recrystallization at 250 °C for 1.0 h, the grains of the sample added 0.1% Ti powder have an obvious grain growth behavior. In contrast, oriented grains caused by deformation have been eliminated, and there is no obvious grain growth in pure Al refined with 0.1% TiN/Ti refiner, indicating that nano TiN in the refiner inhibits the growth of grain during recrystallization.

NANO-MOIRE METHOD

Nano-moiré method presented in this paper is an experimental technique which allows direct measurement of nanoscopic mechanical parameters, such as displacement, strain and dislocation distribution. The basic idea is the formation of moiré fringes when a HREM (high resolution electron microscopy) image of crystal material is superimposed with a unidirectional grating. Fourier filtering technique is used to increase the contrast of fringes and to multiple the fringes. This method has atom-size sensitivity and spatial resolution, and relatively large range. It provides a new experimental technique with very high sensitivity and spatial resolution for nanomechanics.

Higher-order electroelastic modelling of piezoelectric cylindrical nanoshell on elastic matrix

This paper develops electro-elastic relations of functionally graded cylindrical nanoshell integrated with intelligent layers subjected to multi-physics loads resting on elastic foundation.The piezoelectric layers are actuated with external applied voltage.The nanocore is assumed in-homogeneous in which the material properties are changed continuously and gradually along radial direction.Third-order shear deformation theory is used for the description of kinematic relations and electric potential distribution is assumed as combination of a linear function along thickness direction to show applied voltage and a longitudinal distribution.Electro-elastic size-dependent constitutive relations are developed based on nonlocal elasticity theory and generalized Hooke’s law.The principle of virtual work is used to derive governing equations in terms of four functions along the axial and the radial directions and longitudinal electric potential function.The numerical results including radial and longitudinal displacements are presented in terms of basic input parameters of the integrated cylindrical nanoshell such as initial electric potential,small scale parameter,length to radius ratio and two parameters of foundation.It is concluded that both displacements are increased with an increase in small-scale parameter and a decrease in applied electric potential.

微纳米压入测试过程中高熵合金弹性变形对几何必须位错密度的影响

通过微纳米压入法对CoCrFeNiMn高熵合金进行压入测试,得到不同工况下几何必须位错密度与实时压入深度倒数1/h的关系,并探究了弹性因子(Δe)对几何必须位错密度的影响。结果表明,考虑弹性变形影响的几何必须位错密度(ρGe)与1/h呈现出非线性关系;忽略弹性变形影响的几何必须位错密度(ρG)与1/h呈现出线性关系;对比ρG/ρGe随压入深度的变化,发现存在尺度效应:压入深度小于500 nm时,ρG/ρGe比值为3~4,说明弹性因子在浅压痕处对几何必须位错密度影响明显;压入深度达3000 nm时,ρG/ρGe比值接近1;随着压入深度增加,位错滑移逐渐占据主导地位。

Relationship between nano-scale deformation of coal structure and metamorphic-deformed environments

There is a more consanguineous relation be-tween nano-scale deformation of coal structure and meta-morphic-deformed environment. In different metamor-phic-deformed environments, deformation in the coal struc-ture can occur not only at micro-scale, but also at nano-scale, and even leads to the change of molecular structure and nano-scale pore (<100 nm) structure. The latter is the main space absorbing coalbed methane. Through X-ray diffraction (XRD) and liquid–nitrogen absorption methods, the charac-teristics of macromolecular and nano-scale pore structures of coals in different metamorphic-deformed environments and deformational series of coals have been studied. By combin-ing with high-resolution transmission electron microcopy (HRTEM), the macromolecular and nano-scale pore struc-tures are also directly observed. These results demonstrate that the stacking Lc of the macromolecular BSU in tectonic coals increases quickly from the metamorphic-deformed environment of low rank coals to that of high rank coals. For different deformed tectonic coals, in the same metamor-phic-deformed environment, the difference of Lc is obvious. These changes reflect chiefly the difference of different tem-perature and stress effect of nano-scale deformation in tec-tonic coals. The factor of temperature plays a greater role in the increase of macromolecular structure parameters Lc, the influence of stress factor is also important. With the stress strengthening, Lc shows an increasing trend, and La /Lc shows a decreasing trend. Therefore, Lc and La /Lc can be used as the indicator of nano-scale deformation degree of tectonic coals. With increasing temperature and pressure, especially oriented stress, the orientation of molecular structure be-comes stronger, and ordering degree of C-nets and the ar-rangement of BSU are obviously enhanced. For the deforma-tion of nano-scale pore structure, in the same metamor-phic-deformed environment, along with the strengthening of stress, the ratio of mesopores to its total pores volume of tec-tonic coals reduces to a large extent, the ratio of volume of micropores and the pores whose diameters are lower than micropores increases, and sub-micropores and ultra- micro-pores can be found. Moreover, the ratio of specific surface area of mesopores to its total pores reduces rapidly while theamount of sub-micropores increases more quickly. The duc-tile structure coal has a change in pore parameters similar to that of weak brittle deformation. There are differences in the deformation and evolution of nano-scale pore structure of different kinds of tectonic coals formed in different meta-morphic-deformational environments. In short, temperature and confining pressure play some role in the change of nano-scale pore structure parameters, whereas stress has important influence on the evolution of characteristic parameters in nano-scale pore structure of tectonic coals.

Experimental study about nano-deformation field near quasi-cleavage crack tip

Using the nano-moiré method, we measure the near tip nanoscopic deformation on the [111] plane of single crystal silicon with a loaded quasi-cleavage crack running in the [110] direction. The measured strain distribution ahead of the crack tip agrees with the linear elastic fracture mechanics prediction up to 10 nm from the crack tip. Dislocations of Peierls type are detected and they extend from the crack tip over a length of hundreds of Burgers vectors.

再生粗骨料纳米强化处理对混凝土变形性能影响研究

文中采用纳米强化技术对再生骨料预处理,研究纳米强化技术(水玻璃、纳米CaCO 3和纳米SiO 2)对再生混凝土变形性能(干燥收缩、自收缩和徐变)影响;并利用压汞法分析混凝土孔隙结构。结果表明,纳米SiO 2改善再生骨料混凝土变形性能效果最佳,纳米CaCO 3次之,水玻璃效果最差。纳米强化处理可降低再生混凝土孔隙率,优化混凝土孔隙结构。

Temperature-dependent deformation in silver-particle-covered copper nanowires by molecular dynamics simulation

Cu nanowires covered by Ag particles is studied for potential applications in the next-generation microelectronics.To date,the deformation mechanism in the Cu-Ag core-particle is not clear.Here,molecular dynamics simulation is used to describe the Cu-Ag core-particle system.The results show that the equilibrium structure of Ag particles is reconstructed,when the particle≤1.0 nm.At low temperature(1 K)indicate that three different deformation processes take part in the core-particle structure,depending on the size of Ag particles.When the particle diameter≤2.0 nm,the prevailing deformation mechanism is the emission of dislocations from the Cu surface.For the particle diameters ranging from 3.0 to 6.0 nm,the emission of misfit dislocations from the Ag-Cu interface is the dominant deformation mechanism.If the Ag particle≥6.0 nm,the deformation mechanism can be characterized by the slip band,consisting of the dislocations and amorphous atoms.For elevated temperatures(2-400 K),the mechanical properties of the Ag-Cu core-shell system are nearly independent of temperature,whereas the structure with particles larger than 2.0 nm showed a strong dependence of its mechanical properties on temperature.Based on the results,the diameter-temperature plastic deformation map is proposed.

Fabrication of nanostructure in inner-surface of AISI 304 stainless steel pipe with surface plastic deformation

In the present investigation, a pipe inner-surface grinding（PISG） technique was developed to fabricate nanostructure in the inner-surface of an austenitic 304 stainless steel pipe. PISG was performed by high speed shearing with hard sphere tips, leading to gradient distribution of strain, strain rate and strain gradient along depth. Nano-austenite with an average boundary spacing of 20 nm was generated, followed by deformation microstructure characterized by shear bands, multi-and uni-directional twins and planar dislocation arrays. Deformation induced grain refinement of austenitic 304 stainless steel with low stacking fault energy（SFE） covering 4–5 order＇s magnitude of length scales toward nanometer regime was unified.

剧塑性变形制备超细晶/纳米晶结构金属材料的研究现状和应用展望

综合目前剧塑性变形方法制备超细晶及纳米晶结构金属材料的研究现状,介绍等通道转角挤压、高压扭转、累积叠轧焊、多向锻造等剧塑性变形方法及其特点与原理;探讨剧塑性变形金属材料的组织演变和晶粒细化机制;分析金属材料经剧塑性变形后强度与延展性的变化趋势,及其对超塑性变形的影响规律;展望剧塑性变形方法对金属材料应用的前景。

新型纳米三坐标测量机主体结构设计

在分析现有纳米三坐标测量机主体结构的基础上,提出了一种新型的四面对称式桥架结构,并利用ANSYS对主体结构进行分析与对比,从而证明了该结构的优越性。

强化处理对Al_2O_3/SiO_2陶瓷型芯高温变形的影响

研究了强化处理对Al2 O3 /SiO2 纳米复合陶瓷型芯高温变形的影响规律 ,结果表明 :强化处理对Al2 O3 /SiO2 纳米复合陶瓷型芯高温变形的影响很大 ,15 5 0℃保温 1h的高温挠度由强化前的 7mm降至强化后的 1mm。强化剂的浓度对陶瓷型芯高温变形的影响不明显 ,强化次数对陶瓷型芯高温变形的影响相对较大。强化后的陶瓷型芯中出现了莫来石新生片状晶 ,减少了型芯的高温变形。

纳微米聚合物微球的水化膨胀封堵性能

为改善聚合物微球的深度调剖效果,利用蒸馏沉淀聚合法制备纳微米聚合物微球,并利用激光粒度分析仪、微孔滤膜装置和驱替装置对纳微米聚合物微球的粒径、水化膨胀能力和变形封堵能力进行测试分析.结果表明:纳微米聚合物微球为较规则均匀的球形,粒径分布集中,具有良好的水化膨胀性能;随着盐矿化度增大,纳微米聚合物微球膨胀性能变差;随着温度升高,微球的膨胀性能变强;在氯化钙和氯化镁水型中,微球膨胀性能变差;在酸性和碱性环境中,微球膨胀性能变差;随着水化时间增长,微球的封堵性能和变形能力逐渐增强,对孔道产生有效封堵的同时又能变形通过孔道,在渗透率较低的岩心中具有更好的深度调剖效果.

液氮温度下动态塑性形变法制备的纳米孪晶铜结构的研究

利用透射电子显微镜,对液氮温度下动态塑性形变法(LNT-DPD)制备的块体纳米孪晶铜在不同形变量下的微观结构演变进行了研究．结果表明,经LNT-DPD处理后,Cu呈现复杂的微观结构特征：由高密度的纳米尺寸形变孪晶片层团簇、纳米晶组织和含有较高密度位错结构的粗晶组织交错分布组成；其形成机制可归因于形变孪晶与剪切带共同作用的结果．揭示了经LNT-DPD处理的Cu的超高拉伸强度与其微观结构的关系．

纳米钨铜复合材料制备技术的研究进展

阐述了当前纳米钨铜复合材料制备技术的研究进展。从粉末的制备、成形、烧结等方面对传统制备工艺和剧烈塑性变形新工艺进行了论述,并比较了传统的制备工艺和剧烈塑性变形新工艺。

接触测量中的微探球力变形研究

随着微纳米测量系统中测头微探球尺寸的不断减小和测量不确定度要求的不断提高,测力所引起的力变形误差对测量系统不确定度有着不可忽略的影响。根据Hertz理论,构建了微探球与工件接触时的接触模型、微探球与试样力变形模型,给出了最大允许测力估计方法和力变形计算方法。以现有的3种微纳米三坐标测量机微探球为参考,分别估计了允许最大测力及引起的力变形。结果表明,对于纳米量级测量不确定要求,接触式测量中微探球的受力变形误差是不可忽略的。