A Microstructural Approach Toward the Quantification of Anomaly Bond Coat Surface Geometry Change in NiCoCrAlY Plasma-Sprayed Bond Coat

Three-dimensional behavior of NiCoCrAlY bond coat surface geometry change (known as rumpling) was characterized during 120 h of thermal cycling. The proposed scanning electron microscope (SEM)-based 3D imaging method allows for recording the change in both height and width at the same location during the heat treatment. Statistical analysis using both profile information [two dimensions (2D)] and surface information [three dimensions (3D)] demonstrated a typical nature of rumpling as increase in height and decrease in width. However, it also revealed an anomaly of height reduction between 40 and 80 cycles. Such behavior was further investigated by analyzing the bearing area ratio curve of the surface and attributed to filling of voids and valleys by the growth of thermally grown oxide.     

3D laser investigation on micron-scale grain protrusion topography of truncated diamond grinding wheel for precision grinding performance

A grain tip (GT) truncation is proposed to truncate grain protrusion tips of #270 diamond grinding wheel in plunge grinding of hard and brittle material. In this study, a 3D laser microscopy was employed to measure the wheel working surface and parameterize its 3D grain protrusion topography. The objective is to investigate how micron-scale grain protrusion parameters influence grinding performance such as grinding force and surface roughness. First, the GT truncation was performed after dressing of diamond grinding wheel in grinding experiment of quartz glass; then its 3D grain protrusion topography was constructed by smoothing 3D measured noise, matching measured point cloud, transferring protrusion frame and extracting 3D diamond grains; finally, the grain protrusion parameters such as grain protrusion number, grain protrusion height, grain protrusion volume, grain rake angle, grain clearance angle, etc. were investigated in connection with ground surface and grinding force. It is shown that GT truncation averagely decreases grain protrusion number, grain protrusion height, grain protrusion volume, grain rake angle and grain clearance angle by about 44%, 74%, 75%, 24% and 70% on whole wheel surface, respectively. However, it greatly increases active grain number by about 32 times and active grain volume by about 181 times in actual grinding with the depth of cut in 1 μm, thus leading to a decrease (about 80%) in surface roughness and an increase (about 40 times) in grinding force. It is also found that truncated diamond grain tips are mostly shaped with nanometer-scale tip wedges along grain cutting direction, leading to about 75% very large negative grain rake angles and about 75% large grain clearance angles, thus contributing to ductile-mode grinding. It is confirmed that the active grain number and active grain volume for the actual depth of cut may be regarded as main grain protrusion parameters to evaluate and predict the precision grinding performance of a coarser diamond grinding wheel.     

粗糙表面弹塑性加卸载多级接触模型

真实工程表面在微观尺度上都是粗糙的,它们之间的接触实际上是表面微凸体的接触,粗糙表面间的接触行为对接触部件的真实承载能力、摩擦磨损等性能都有重要影响,研究工程表面间的真实接触行为是摩擦学研究的主要内容之一。采用最小均方误差法得到表面轮廓抛物线拟合曲线,在最大限度近似原始表面轮廓的同时,该方法能够更好地适用于微凸体弹塑性接触加卸载模型。通过单个微凸体上的支承载荷将总体级别模型和微凸体级别模型相联系,建立粗糙表面多级接触加卸载模型。以柱面与平面接触为算例,将接触区域视为与圆柱母线平行的离散线条集合,得到微凸体法向变形量和粗糙表面真实接触面积,该模型可用于分析粗糙表面弹塑性加卸载的真实接触行为。     

Non-Gaussian effects in microcontact

The two parameter Weibull distribution is proposed as a model for asperity heights. Unlike the symmetrical gaussian model usually assumed, it is capable of accounting for skewness, either positive or negative, in the asperity height distribution.The Weibull parameters are shown to be readily determined numerically for a given RMS level and dimensionless skewness of the asperity height distribution. In addition the contact of two Weibull surfaces may be approximated as the contact of an equivalent single Weibull surface and a smooth plane.Using results obtained by simulation it is shown that for the same RMS height the mean asperity pressure can be higher than in the gaussian case by a factor of 1.4 if the skewness is +1 and lower by a factor of 1.7 if the skewness is −1.     

钛合金氧碳共渗层性能

将经磨平、抛光、超声波乙醇清洗、吹干的Ti6Al4V合金样品放入专用设备中进行氧碳共渗。分别采用X射线衍射仪（XRD）、扫描电子显微镜（SEM）、能谱仪（EDS）、HV硬度仪、万能材料试验机对渗层的物相、显微组织形貌、成分、硬度、摩擦磨损、力学性能进行分析。XRD结果表明,渗层中出现TiC和TiO_x相。氧碳共渗改变了原Ti6Al4V合金的组织,渗层的显微组织明显区别于Ti6Al4V的渗碳、渗氧以及在CO₂气氛下处理的组织。EDS结果表明,C、O元素含量呈现梯度变化。相比基体硬度,渗层表面硬度提高了3.8倍,渗层硬度呈梯度变化。氧碳共渗改变了原始样的粘着磨损和摩擦状态,渗层样表面只有轻微的摩擦痕迹、无磨损。氧碳共渗后磨损量是原始样的3.5%,摩擦系数约为原始样的30%。渗层样在拉断过程中,外表面有一定的剥落,表面布满裂纹,样品的强度略有下降,断面延伸率和断面收缩率与原始样相当。Ti6Al4V合金经过氧碳共渗后,提高了表面硬度,降低了磨损率和摩擦系数,基本保持了基体的力学性能。     

激光冲击对690高强钢表面完整性的影响

为研究激光冲击处理对690高强钢表面完整性的影响,采用不同功率密度的脉冲激光冲击690高强钢试样,借助光学轮廓仪、X射线应力仪、硬度计和透射电镜,测试分析激光冲击前后690高强钢试样的表面三维形貌、硬度、残余应力和微观组织的变化。结果表明:不同功率密度的激光冲击后,690钢的表面粗糙度增大;随着激光功率密度的增加,试样表面轮廓的最大高度R_y从1.814 μm增至3.247 μm。不同功率密度的激光冲击后,试样残余应力均值由－122 MPa增加至－296 MPa,显微硬度的均值由277 HV0.1 增加至355 HV0.1。与未进行激光冲击强化试样相比,激光冲击处理使690高强钢试样表层晶粒不断细化,且功率密度越大表层晶粒尺寸越小。     

表面刻蚀粉末冶金黄铜的微观结构和防结蜡性能研究

目的原油运输中管道结蜡问题严重影响正常的生产运输,通过表面刻蚀的方法,获得具有超亲水性的粉末冶金黄铜表面,从而达到良好的防结蜡性能。方法结合不同刻蚀时间下的表面微观结构、粗糙特性和润湿特性,对防结蜡性能进行系统研究。采用Fe Cl3溶液,刻蚀粉末冶金黄铜试样不同时间,通过X射线衍射仪和扫描电子显微镜对刻蚀表面的成分和形貌进行分析,利用接触角测量仪测量样品表面润湿性,最后对刻蚀后的黄铜进行防结蜡测试。结果表面刻蚀过程实为"脱锌",在试样表面形成了微纳米级颗粒粗糙结构。随着刻蚀时间的延长,最大轮廓高度Rz相应增大。与未刻蚀试样相比,刻蚀后的试样表面水接触角大幅降低,防结蜡性能显著提升。当刻蚀时间为120 min时,水接触角远小于30°,粉末冶金黄铜表面达到超亲水状态,防结蜡测试后,约80%表面为干净的原始表面,几乎没有石蜡吸附。结论刻蚀表面的亲水成分和棱锥状铜单质颗粒组成的微细粗糙结构,使得其在水相中形成稳定的"水膜",这层水膜可以有效阻止油相中石蜡的析出与沉积,达到良好的防结蜡效果。     

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实验室模拟了不同热送热装温度的Ti微合金化连铸坯热送热装和加热过程,并采用光学显微分析、扫描电镜分析和透射电镜分析等方法,观察了生产条件下连铸坯和粗轧中间坯试样的显微组织,以及实验室条件下不同热履历铸坯试样的显微组织,分析了热送热装连铸坯在粗轧过程中表面裂纹的生成原因。结果表明,经热送热装的连铸坯表面金属中奥氏体晶界处的先共析铁素体膜及沿奥氏体晶界的碳氮析出物可能是导致粗轧过程表面裂纹形成的主要原因。     

深冷处理对TC4钛合金表面性能的影响

研究了深冷处理对TC4钛合金滚磨光整加工和表面性能的影响。对TC4钛合金试样进行深冷处理,将不同深冷时间下的试样进行滚磨光整加工,根据表面粗糙度确定适合的深冷时间后,对比分析深冷处理前后合金试样的显微组织、显微硬度及残余应力的变化。利用扫描电镜探究了深冷处理和滚磨光整加工后合金试样表面形貌的变化。结果表明,深冷处理12 h后试样表面粗糙度最小,试样组织受到冷缩内应力的作用,α相的比例从未深冷处理的56.45%增加到85.42%,组织变得均匀且致密。试样的显微硬度在深冷处理12 h时最大,比未处理试样提高了3.47%。深冷处理12 h和滚磨光整加工后的试样相比未处理试样表面残余压应力增加26.26%。粗糙度测量和扫描电镜结果显示深冷处理使钛合金试样的可加工性增强,深冷处理12 h的试样经过离心式滚磨光整加工表面粗糙度可从约0.500 μm下降到约0.250 μm,表面质量明显变好。     

直接激光沉积Fe-Cr-Ni梯度合金钢的组织与性能

采用直接激光沉积技术制备了具有外强内韧组织性能的12CrNi2Y-50Cr6Ni2Y-70Cr8Ni2Y梯度合金钢试样,利用光学显微镜、扫描电镜、透射电镜、硬度计、摩擦试验机等分析手段,对直接激光沉积的梯度合金钢试样的组织结构、界面结合性、硬度梯度分布及耐磨性等进行了研究。结果表明,在优化的激光沉积参数下,成功制备出了无裂纹夹杂缺陷、梯度过渡界面处呈现冶金结合的12CrNi2Y-50Cr6Ni2Y-70Cr8Ni2Y梯度合金钢试样。梯度合金钢的组织呈现出由粒状贝氏体+板条贝氏体+少量马氏体→板条贝氏体+板条马氏体→板条马氏体+片状马氏体的变化趋势,对应硬度呈356 HV0.2→551 HV0.2→712 HV0.2梯度分布,体积磨损率呈现2.01×10^-4 mm³·N^-1·m^-1→1.33×10^-4 mm³·N^-1·m^-1→0.71×10^-4 mm³·N^-1<...     

贝氏体表面浮凸及其形成机制

将3mm厚的工业用60Si2Mn、60Si2CrV和22MnCrNi钢试样抛光后在真空炉中加热到1100℃奥氏体化，保温40min，炉冷。不经浸蚀，分别采用QUANTA-400环境扫描电镜、Nanofrist-1000扫描隧道显微镜和光学显微镜观察试样，发现，贝氏体相变过程中产生了表面浮凸，表面浮凸为“帐篷形”（“A”型），并认为贝氏体表面浮凸的产生，是由于过冷奥氏体转变为贝氏体时比体积增大，且试样表面层体积膨胀不均匀造成的。     

The robust detection and removal of unwanted asperities in applied surface metrology

The presence of unwanted asperities or debris in surface metrology data is a problem faced by many manufacturers of high volume precision components. The process of re-cleaning and re-measurement upon detection of an asperity can be extremely time consuming and costly. Current asperity removal methodologies are significantly limited due their fixed formats and to the user selection of thresholds. This paper presents an adaptive method of detection and an accompanying procedure for padding across the removal area. Results are presented for asperity removal in the measurement of roundness on fuel injector components.     

Fe-15Ni-0.6C合金马氏体浮凸及相变新机制

对预先抛光的Fe-15Ni-0.6C合金试样进行真空热处理,随后用Nano First-1000型扫描隧道显微镜和QUANTA-400型环境扫描电镜对未经浸蚀的试样进行观察分析,发现,Fe-15Ni-0.6C合金马氏体片的浮凸为帐篷形（∧型）,浮凸最高高度为43~96 nm。分析认为,马氏体表面浮凸是由于过冷奥氏体转变为马氏体时比体积增大、体积膨胀造成的,而非切变所致。对浮凸高度进行了理论计算,结果表明,马氏体线膨胀量比实测的浮凸高度大,计算的浮凸平均高度为162 nm,是膨胀过程受阻所致。浮凸非N形,是帐篷形,不具备切变特征,马氏体的切变机制缺乏实验依据,也与实际不符。提出了马氏体相变新机制。     

Martensitic stainless steel modified by plasma nitrocarburizing at conventional temperature with and without rare earths addition

17-4PH Martensitic stainless steel was plasma nitrocarburized at conventional temperature (560 °C) with and without rare earths (RE) addition. The surface treated layers were characterized by optical microscope, scanning electron microscope equipped with an energy dispersive X-ray analyzer, X-ray diffraction and microhardness test. The wear and corrosion behavior of the modified specimens was studied respectively using pin-on-disc tribometer and anodic polarization tests. The results show that rare earths atoms can diffuse into the surface of the stainless steel. The microstructures of all modified layers are characterized by a compound layer containing three distinct zones but without an evident diffusion zone. The phases on all modified surface layers are mainly of θ-Fe₃C and CrN. It is exciting that the hardness profile of the modified layer is decreased gradually, which is rarely found in plasma nitriding of the stainless steel. The friction coefficient of a specimen can be dramatically decreased by plasma RE nitrocarburizing, whereas the corrosion resistance is deteriorated. In contrast, the corrosion resistance of a plasma nitrocarburized specimen is enhanced but the friction coefficient is not improved as much as that of a plasma RE nitrocarburized one.     

The Electron Microscope in the Study of Paints

A brief account is given of the theory of the electron microscope and the special specimen techniques that are employed A method of mounting pigments and a surface replica technique for paints is described.

Applications of the electron microscope in the study of pigments and extenders, surface characteristics of paints and varnishes, and the internal structure of paints are described. The size and shape characteristics of pigments, the relation between surface contour and gloss and the nature of various forms of bloom are discussed. Examples are given of the use of the electron microscope in studying surface changes during natural and artificial weathering. The use of thin sectioning techniques in the study of the location of pigment particles in paint films is described.     

空心铝型材挤压过程计算机仿真系统

试开发了一套基于计算机辅助设计和数值模拟的空心铝型材挤压过程计算机仿真系统,它涵盖了模具工艺设计的全过程,可以集成原有的和新建立的工艺设计知识。该系统包括空心型材挤压模具及坯料的参数化几何造型模块,并能分析分流桥的截面形状、分流孔的布置、焊合室的高度、工作带长度和阻流或者助流结构对金属流速分布的影响,模具的弹性变形对工作带有效长度和模孔尺寸的影响。     

多晶体钛拉伸变形表面褶皱的形成及晶粒变形

用原子力显微镜对多晶体钛拉伸塑性变形中表面褶皱的形成及单个晶粒的变形进行了连续观察和测量.结果表明,表面褶皱随着应变量的增加而增大,而凹凸的相对位置关系不随变形的进行而变化.从单个晶粒来看应变量在0.1附近时由于孪晶的形成产生了新的凹凸,但对整体的表面褶皱凹凸位置关系没有大的影响.表面平均粗糙度和表面最大高低差随应变量的增加近似呈直线性增大,应变量在0.1左右时由于孪晶的形成,使粗糙度有较明显的增大.     

In-situ observation on domain switching of PLZT via Raman spectroscopy

1 Introduction Domain switching is considered a major cause for degradation and failure of ferroelectric materials[1?3]. Observation of domain switching in the materials is an important way to investigate mechanism for degradation and failure of ferroele…     

Barreling of a short cylinder in compression

Large deformation behaviour of aluminium and low carbon steel short cylinders of various diameters and height to diameter ratios, loaded axially in a simple compression test without using any lubricant, is examined. Typical histories of deformation of the cylindrical surface and the end face are presented with a view to studying the nature and the extent of free surface barreling, its folding into the end face and effects of specimen size thereon. The results reveal that the profile of a deforming specimen can sensibly be approximated by an arc of a circle only after the onset of folding.     

Surface modification of cyclic olefin copolymer substrate by oxygen plasma treatment

Cyclic olefin copolymer (COC) substrate surface was modified by plasma treatment under oxygen atmosphere. The surface properties were evaluated by contact angle measurement, atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). It was found that the surface acquired oxygen containing polar functional groups such as C-O, C = O, which increased in number as the plasma treatment time increased. As revealed by AFM profile, these changes were accompanied by a slightly increase in roughness. The adhesive ability between the coating layer (ITO) and the COC surface can be improved after optimum plasma treating procedure, which can be proofed by the optical microscope observation after boiling test.