Grain size measurement by EBSD in complex hot deformed metal alloy microstructures

The measurement of grain size by EBSD has been studied to enable representative quantification of the microstructure of hot deformed metal alloys with a wide grain size distributions. Variation in measured grain size as a function of EBSD step size and noise reduction techniques has been assessed. Increasing the EBSD step size from 5% to 20% of the approximate mean grain size results in a change in calculated arithmetic mean grain size of approximately 15% and standard noise reduction techniques can produce a further change in reported size of up to 20%. The distribution of measured grain size is found not to be log‐normal, with a long tail of very small sizes in agreement with a computer simulation of linear intercept and areal grain size measurements through randomly oriented grains. Comparison of EBSD with optical measurements of grain size on the same samples shows that, because of the ability of EBSD to distinguish twins and resolve much smaller grains a difference of up to 50% in measured grain size results.     

Temperature measurement in orthogonal metal cutting

Orthogonal cutting experiments were carried out on steel at different feedrates and cutting speeds. During these experiments the chip temperatures were measured using an infrared camera. The applied technique allows us to determine the chip temperature distribution at the free side of the chip. From this distribution the shear plane temperature at the top of the chip as well as the uniform chip temperature can be found. A finite-difference model was developed to compute the interfacial temperature between chip and tool, using the temperature distribution measured at the top of the chip.Nomenclature contact length with sticking friction behaviour [m] - c specific heat [J kg^–1 K^–1] - contact length with sliding friction behaviour [m] - F _P feed force [N] - F _V main cutting force [N] - h undeformed chip thickness [m] - h _c deformed chip thickness [m] - i,j denote nodal position - k thermal conductivity [W m^–2 K^–1] - L chip-tool contact length [m] - p defines time—space grid, Eq. (11) [s m^–2] - Q _C heat rate entering chip per unit width due to friction at the rake face [W m^–1] - Q _T total heat rate due to friction at the rake face [W m^–1] - Q _% percentage of the friction energy that enters the chip - q ₀ peak value ofq(x) [W m^–2] - q _e heat rate by radiation [W] - q(x) heat flux entering chip [W m^–2] - t time [s] - T temperature [K] - T _C uniform chip temperature [°C] - T _max maximum chip—tool temperature [°C] - T _mean mean chip—tool temperature [°C] - T _S measured shear plane temperature [°C] - x,y Cartesian coordinates [m] - V cutting speed [m s^–1] - V _C chip speed [m/s] - rake angle - ,, control volume lumped thermal diffusivity [m² s^–1] - emmittance for radiation - exponent, Eq. (3) - density [kg m^–3] - Stefan-Boltzmann constant [W m^–2 K⁴] - (x) shear stress distribution [N m^–2] - shear angle     

Lattice constant measurement from electron backscatter diffraction patterns

Kikuchi bands in election backscattered diffraction patterns (EBSP) contain information about lattice constants of crystallographic samples that can be extracted via the Bragg equation. An advantage of lattice constant measurement from EBSPs over diffraction (XRD) is the ability to perform local analysis. In this study, lattice constants of cubic STN and cubic YSZ in the pure materials and in co‐sintered composites were measured from their EBSPs acquired at 10 kV using a silicon single crystal as a calibration reference. The EBSP distortion was corrected by spherical back projection and Kikuchi band analysis was made using in‐house software. The error of the lattice constant measurement was determined to be in the range of 0.09–1.12% compared to values determined by XRD and from literature. The confidence level of the method is indicated by the standard deviation of the measurement, which is approximately 0.04 Å. Studying Kikuchi band size dependence of the measurement precision shows that the measurement error decays with increasing band size (i.e. decreasing lattice constant). However, in practice, the sharpness of wide bands tends to be low due to their low intensity, thus limiting the measurement precision. Possible methods to improve measurement precision are suggested.     

轻金属合金的高速加工

1．引言 高速加工技术是极具潜力的先进制造技术,但是,它从理论概念到工业化经过了大约60年的时间,这主要是因为在初始研究阶段当时的生产设备无法满足高速加工的要求。     

双金属核壳纳米结构中荧光单分子的表面能量转移及金属操控自发辐射效应

贵金属表面附近的荧光分子因其表面等离子体共振的影响,荧光发射特性发生显著变化,被广泛应用在荧光探针等纳米器件的设计、开发中。荧光分子与金属之间的能量转移机制是设计此类荧光探针的基础。使用时域有限差分(FDTD)方法,对Au/SiO₂/Ag核壳纳米复合结构的等离子体杂化场中荧光单分子的表面能量转移(SET)效应和金属操控自发辐射效应进行了理论仿真研究。研究了金核和银壳共同作用时,荧光分子的SET和金属调控自发辐射过程随荧光分子位置及分子偶极矩取向的变化规律。计算结果表明,由于金核和银壳之间的局域表面等离子体共振杂化耦合,荧光分子与金属间的能量转移效率与距离d呈现出10次方的关系,这一结果明显区别于常规的荧光共振能量转移(FRET)效应,较之单金属结构的SET效应更加剧烈。这一结果有希望在生物光子学领域的纳米级局域光源的创建和生物分子的检测中得到应用。     

Pulse current-assisted hot-forming of light metal alloy

Pulse current-assisted hot-forming (PCAHF) of light metal alloy is developed due to lower energy consumption and higher efficiency. In this process, the metal sheet is designed in series in a pulse current circuit and heated directly by the pulse current. In addition, the ceramics mold is employed to avoid the heating current leaking. The Ti-6Al-4 V sheets are employed to improve the temperature distribution of the heated light metal alloy sheet. The effects of effective current density on the temperature and the rate of increase in temperature are studied by the pulse current heating experiment, and the effect of duty ratio on the forming property is studied by the forming experiments. Moreover, some light metal samples with different shapes are formed by the method of PCAHF. As the results, the hot forming with the merits of high-efficiency and low-energy consumption becomes possible.     

Microscale mechanisms of ultrasound velocity measurement in metal melts

Ultrasound Doppler velocimetry (UDV) is a powerful, widely used technique for measuring flow in metal melts. However, UDV in metal melts suffers from substandard reliability because its operation depends on phenomena that are poorly understood. In this study, we investigate the poorly characterized source of bulk echoes in metal melts and the corresponding mechanisms of ultrasound signal deterioration. We present evidence from electron microscopy and ultrasound measurements that oxide inclusions are the main source of bulk echoes in gallium. By measuring their terminal velocity, we estimate the mean size of echoing objects in gallium to be 58–64 μm, implying that Mie scattering is the dominant scattering mechanism. By comparing UDV measurements in which signals were transmitted directly into the fluid, to others in which signals were transmitted through a vessel wall, we show evidence that there are two distinct mechanisms for signal degradation: the loss of echoing objects from the bulk and the deterioration of acoustic coupling and wetting at the transducer surface. We suggest stirring vigorously and using indirect-contact UDV measurement strategy to mitigate the signal degradation in metal melts.     

Principles of optimizing additive compositions to mesogenic compounds of metal working LCA

Optimization principles are proposed for composing additives to mesogenic compounds of LCA used for metal working structural steels. The considered additives were found to positively affect the drilling process. The problems of their use in practice are discussed.     

GaBi alloy liquid metal ion source for microelectronics research

A GaBi alloy liquid metal ion source has been studied. From an analysis of the source mass spectra as a function of emission current, a mechanism is suggested for the production of single- and double-charged ions. There is good agreement with the results of Swanson's investigations of a pure Bi source.     

一种新型的高炉铁水液面计量系统

本文介绍高炉铁水称重液面计量系统,针对系统特点,着重描述了称重装置、电气装置及隔热保护装置等方面采取的改进措施,从而达到了称量准确、液面控制可靠的目的.     

Interactions and effects of metal oxide nanoparticles on microorganisms involved in biological wastewater treatment

To clarify the toxicological effects of metal oxide nanoparticles (NPs) on microorganisms with environmental relevance, it is necessary to understand their interactions. In this work, they were studied the effects and the morphological interactions of two metal oxide NPs (ZnO and TiO₂) with microorganisms, during aerobic treatment of wastewater. The effects were evaluated according to nutrient removal from wastewater, while morphological interactions were determined by three different techniques such as TEM, HAADF‐STEM, as well as an elemental mapping. According to results about effects of both NPs, they inhibited the removal of organic matter and ammonia nitrogen, and enhanced the orthophosphate removal. Related to morphological interactions, the electron‐dense material of both NPs was mainly observed bounded to cell membrane. In tests with ZnO NPs, it was also observed electron‐dense material internalized in microorganisms without physical damage in cell membrane. The elemental mapping was useful to determine that the electron‐dense material corresponded to Zn and Ti. Both interactions, internalization and attachment of NPs on cell membrane of microorganisms may trigger the negative effect in the removal of organic matter and nitrogen.     

Optimization of semi-solid metal processing of A356 aluminum alloy

Semi-solid metal (SSM) processing has been recognized as an advanced process to produce high-quality and low-cost engineering components. The cooling slope method is a simple route that can develop non-dendritic slurry for various purposes with reduced equipment and processing costs. In this study, the cooling slope method was employed to produce the A356 feedstock in SSM processing. The dendritic primary phase in the conventionally cast A356 alloy has transformed into a non-dendritic one through the use of ingots cast over a cooling plate with a different pouring temperature. After pouring, the melt that becomes semi-solid at the end of the plate is consequently poured into cylindrical steel molds with different mold temperatures. Also, the process has been conducted in different cooling slopes and different cooling lengths. Then, a back-propagation neural network has been designed to correlate the process parameters to grain size. Finally, genetic algorithm (GA) has been used to optimize the process parameters. Results indicate that the pouring temperature, mold temperature, cooling slope, and cooling length have significant effects on size and morphology of α-Al phase. The GA can optimize the process as well.     

Liquid metal alloy ion source based metal ion injection into a room-temperature electron beam ion source

We have carried out a series of measurements demonstrating the feasibility of using the Dresden electron beam ion source (EBIS)-A, a table-top sized, permanent magnet technology based electron beam ion source, as a charge breeder. Low charged gold ions from an AuGe liquid metal alloy ion source were injected into the EBIS and re-extracted as highly charged ions, thereby producing charge states as high as Au(60 +). The setup, the charge breeding technique, breeding efficiencies as well as acceptance and emittance studies are presented.     

一种新型机械零件表面形貌测量仪的研究

介绍了基于象散法的激光自动聚焦原理,论证了利用该原理在金属表面微位移测量技术中的应用,可通过对自动聚焦伺服系统各信号的控制来进行表面形貌的测量.研究并开发了一台基于已有光驱激光头及其伺服电路的经济型三坐标测量仪,使用步进电机带动丝杠传动实现X、Y轴的进给,通过改变步进电机驱动器细分数改变进给步长,读取聚焦良好时音圈电机的加载电压作为该点的Z坐标值.     

金属构件残余应力测量技术进展

残余应力是消除外力或不均匀的温度场等作用后仍留在物体内的自相平衡的内应力,对构件的力学性能有显著影响,会引起零件发生翘曲或扭曲变形,甚至开裂,定量测量残余应力数值对改变构件疲劳寿命,预防构件发生脆性破坏具有重要意义。国内外对残余应力测量进行了深入的研究,提出了多种测试方法。详细介绍了有损及无损残余应力测量技术的测量原理及国内外目前研究现状,分析总结了影响测试精度的主要因素及改进方法;调研了目前市场上较先进的仪器设备及其供应厂家;针对盲孔法孔周围塑形变形及钻孔偏心、压痕法塑性区域半径、X射线衍射法试样内部显微组织结构、中子法零点漂移、超声波法测量尺寸带来的误差的重要改进技术;并对残余应力测量技术发展方向进行了展望。     

激光刻蚀金银合金胶体的制备及其SERS应用

金属胶体是一种新兴的表面增强拉曼散射(SERS)活性衬底,利用激光液相刻蚀技术制备了金银合金胶体,并通过透射电镜、吸收光谱、表面增强拉曼散射光谱等手段对其特性进行表征。结果表明,合金粒子多数为球形颗粒,颗粒大小在5nm左右,并且有很好的分散性,等离子体共振吸收峰位于428nm。此外,该胶体表现出很好的表面增强拉曼散射活性,且性能稳定可在室温下长时间保存。