纳米晶精密电铸技术的研究

采用高频脉冲电流、高速冲液及加入有机添加剂等细化晶粒方法，开展了纳米晶精密电铸技术的试验研究。分析、研究了过程参数及添加剂对沉积层的晶粒尺寸及微观硬度和耐腐蚀性的影响。结果表明，采用上述细化晶粒方法，可制备出晶粒最小尺寸为20nm的电铸沉积层；随着晶粒尺寸的减小，沉积层微观硬度和耐腐蚀性能得到了明显提高。     

纳米复合材料的微细电铸技术研究

为提高电铸微器件的力学性能,研究了镍-纳米氧化铈颗粒复合电铸工艺,分析了电铸参数(电流密度、纳米氧化铈颗粒浓度及转速)对沉积层中纳米氧化铈颗粒含量、沉积层微观结构及织构、沉积层微观硬度的影响.试验结果表明,电流密度对沉积层中纳米氧化铈颗粒含量具有重大影响.由于纳米氧化铈颗粒的加入,使得沉积产物的晶粒细化,择优取向由(220)逐步转变为(111),微观硬度显著增强.     

纳米晶粒精密电铸层力学性能的试验研究

采用高频窄脉宽脉冲电流、高速冲液等方法获得金属镍纳米晶粒精密电铸层。分析、研究了晶粒大小对沉积层力学性能的影响。结果表明,随着晶粒尺寸的减小,沉积层微观硬度和强度性能得到了明显提高。常温条件下,沉积层晶粒从1 000 nm细化至70 nm时,其抗拉强度可提高至1 160 Mpa,但随着沉积层晶粒进一步细化,其抗拉强度呈下降趋势,出现与传统的Hall-Patch理论相背离现象。200 ℃时,得到和常温条件下类似结果,而400 ℃时,其抗拉强度随着晶粒的细化基本保持不变。     

基于纳米氧化镧的精密电铸工艺试验研究

采用纳米稀土La2O3为添加剂，研究其对电铸镍溶液特性、铸层微观结构及其性能的影响。通过对沉积过程中阴极极化曲线的测定，探讨了纳米La2O3在电极表面的作用机理，并采用SEM、XRD等现代分析手段对电铸层微观结构进行了测试和分析。试验结果表明：纳米La2O3能够在阴极表面发生特性吸附，增大阴极极化，细化精密电铸层晶粒，提高铸层的均匀性；晶粒生长在（220）晶面方向上存在明显的择优取向；获得的电铸层显微硬度比普通电铸层有显著提高。     

镍锰合金的纳米晶电铸

电铸镍锰合金因其特殊的性能而具有重要的应用前景。分析了电沉积纳米晶材料的原理 ,在此基础上采用高速冲液、直流和高频脉冲电流以及电解液中加入添加剂等方法进行了镍锰合金的电铸试验 ,并对电铸层的锰含量、表面形貌和晶粒尺寸进行了测试。试验结果实现了镍锰合金的纳米晶电铸。讨论了锰含量、电流密度和添加剂等因素对电铸层晶粒尺寸和表面形貌的影响。     

纳米晶脉冲电铸的试验研究

通过理论分析和试验研究 ,利用高频脉冲电流、高速冲液及添加剂方法 ,获得了纳米晶电铸层。分析了在脉冲电铸过程中 ,电规准及添加剂对沉积层微观结构影响     

脉冲电铸镍-氧化钕纳米复合沉积层的工艺研究

电化学沉积层的制备是电铸技术的关键环节。本文采用脉冲电铸技术制备N i-Nd2O3纳米复合沉积层,考察了镀液中Nd2O3纳米颗粒添加量、平均电流密度、占空比、脉冲频率对纳米复合沉积层中Nd2O3含量及纳米复合沉积层显微硬度的影响,并对纳米复合沉积层的表面形貌进行了分析。结果表明,在镀液中Nd2O3纳米颗粒添加量20 g/L~30 g/L、脉冲平均电流密度2 A/dm2~4 A/dm2、占空比0.2~0.4和脉冲频率1000 Hz的条件下,可获得Nd2O3含量大的高硬度复合沉积层,并且沉积层表面平整、光滑,晶粒细小,组织均匀致密。     

Ni-ZrO2纳米复合电铸层表面形貌、组织结构及性能研究

通过复合电铸工艺制备Ni-ZrO2纳米复合电铸层,探讨了镀液中纳米ZrO2颗粒悬浮量和电流密度对Ni-ZrO2纳米复合电铸层表面形貌的影响,用SEM、TEM和显微硬度仪对纳米复合电铸层的表面形貌、组织结构和显微硬度进行了分析。结果表明,镀液中纳米ZrO2颗粒悬浮量和电流密度对纳米复合电铸层表面形貌有较大程度的影响。纳米ZrO2颗粒细化了复合电铸层中基质金属的晶粒,使复合电铸层的表面光滑平整,组织均匀、致密,显微硬度大幅度提高。     

射流电铸快速成型纳米晶铜的组织与性能

采用射流电铸快速成型方法制备了纳米晶铜铸层,并用SEM、XRD等方法对纳米晶铜铸层表面形貌、微观组织结构以及晶粒大小进行了分析,对纳米晶铜铸层的力学性能进行了测试.结果表明:在电铸电流密度为300 A·dm-2时,制备的纳米晶铜平均晶粒尺寸为47.4 nm,纳米晶铜铸层的抗拉强度为470 MPa,伸长率为14%,抗拉强度是粗晶铜的3.6倍.     

磨擦辅助对电铸镍组织结构的影响

在电铸镍的过程中,由于电沉积机理的复杂性,电铸层的组织结构受多重工艺参数的影响,且还需解决镍电铸层存在针孔和结瘤等缺陷的问题。采用磨擦辅助电铸技术进行电铸镍,可以有效抑制电铸层缺陷的产生,在设计的试验装置上,制备了不同微观组织结构的镍电铸层。研究了磨擦强弱对镍电铸层的表面形貌、织构等微观结构的影响。结果表明:在磨擦辅助电铸镍过程中,随着阴极表面线速度的提高,游离微珠对电铸层的整平作用和晶粒细化作用相应增强。旋转阴极在不同的线速度条件下,可以制备出大范围不同微观结构的镍电铸层,其晶粒尺寸在(100~600)nm之间。随着阴极速度的提高,镍电铸层各晶面的相对生长速率差别变小。     

单晶蓝宝石的延性研磨加工

为实现单晶蓝宝石的延性研磨加工,采用纳米压痕和划痕法测试并分析了单晶蓝宝石(0001)面的微纳力学特性,建立了单颗圆锥状磨粒的压入模型并计算了延性研磨加工的受力临界条件,分析了金刚石磨粒嵌入合成锡研磨盘表面的效果.对单晶蓝宝石进行了延性研磨加工试验,采用NT9800白光干涉仪、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等方法分析了单晶蓝宝石的延性研磨表面特征.试验结果表明:采用纳米压痕和划痕法可以为单晶蓝宝石的延性研磨加工提供工艺参数,单晶蓝宝石的延性堆积的极限深度为100 nm,金刚石磨粒的嵌入及在适当载荷下可以实现蓝宝石的延性研磨加工,实验条件下的最佳载荷为21 kPa,延性研磨后单晶蓝宝石表面划痕深度的分布情况较好,分散性小,研磨后的表面发生了位错滑移变形.     

INVESTIGATION INTO THE CHARACTERISTICS OF WHITE LAYERS PRODUCED IN A NICKEL-BASED SUPERALLOY FROM DRILLING OPERATIONS

The nature of white layers generated during metal cutting operations have for some time been the object of scientific controversy in reference to their metallurgical nature/structure. This research aims to study the structure of the white layer from an abusive cutting operation (i.e., drilling) in a nickel-based superalloy at both macro and micro scale levels. This has been achieved by using (1) a Focus Ion Beam to mill a sample for Transmission Electron Microscopy to analyse the grain size within the white layer, (2) Scanning Electron Microscopy to see shape characteristics of the white layer generated, (3) X-ray diffraction to see any alterations to the crystallinity of the structure, and (4) nano-indentation within this layer to compare its hardness with that of the bulk material. The in-depth analysis of white layers generated from non-standard drilling parameters of alloy RR1000 has shown that the layer is of the same structure as the bulk material: face centre cubic (FCC). The analysis has also shown the layer possesses a greatly reduced grain size of approximately 50 nm as opposed to the bulk material which has an average grain size of 22–63 μm (ASTM 8-5). Although nano-indentation has also shown that the analysed layer has a 45% higher hardness than that of the bulk material. This analysis indicates that the white layer created from machining is a combination of both mechanical and thermal effects and not only thermal as previously shown.     

微波等离子体CVD法在非平面基体上生长金刚石膜

介绍了在微波等离子体CVD装置中,用甲烷和氢气作为原料,在非平面基体(如钨丝、钻头、铣刀等)上生长金刚石薄膜的研究。在金刚石沉积过程中,由于"尖端效应",在基体的尖端很难沉积出金刚石膜。在采用金属丝屏蔽后,克服了"尖端效应",成功地在非平面基体上沉积出了金刚石膜。用扫描电镜(SEM)和激光拉曼光谱(Raman)分析了金刚石膜的形貌和质量。结果表明:非平面基体不同位置金刚石的晶形不同,晶粒比较细小,膜的质量较高。     

直流脉冲电流对7475铝合金超塑性变形中位错运动的影响

研究了直流脉冲电流对7475铝合金超塑性拉伸时的力学性能的影响。结果表明：脉冲电流能显著提高7475铝合金的伸长率，稍微降低其变形流动应力。透射电镜观察发现晶内位错从杂乱无章的状态调整到顺电子流动的方向，各位错段相互平行排列；移动到晶界处的位错能继续以滑移-攀升的方式协调晶界处的变形。由于在超塑性变形中，晶界的变形占据主导地位，电子风在晶界处推动位错的运动，比在晶内的作用更能有效地提高7475铝合金的伸长率。     

Reflection electron microscopy (REM) of fcc metals

Reflection Electron Microscopy (REM) using diffracted beams from bulk specimens is shown to be possible with commercial electron microscopes. Surface images have been recorded from single crystal Au and Pt(111) surfaces. These images reveal growth steps, dislocations, slip traces, and other features. Geometrical restoration has been made of foreshortened images, and analysis of image contrast shows the importance of out-of-focus phase contrast and the diffraction contrast from strain fields.     

Novel combination of orientation measurements and transmission microscopy for experimental determination of grain boundary miller indices in silicon and other semiconductors

The determination of grain boundary planes in multicrystalline material has only been restricted to transmission electron microscope investigations (Jang et al., 1992; Elgat et al., 1985) or to metallograpical investigations of the grain boundary (Randle et al., 1993). The first method is expensive, and both are complex and time consuming in grain boundary preparation. This paper proposes the determination of grain boundary planes in semiconductor wafer by a combined application of Electron Back Scatter Diffraction and Infrared Transmission Microscopy. In particular, the new method is demonstrated with directional solidificated multicrystalline silicon.     

A ‘3-body’ abrasion wear study of bioceramics for total hip joint replacements

The current study focuses on the effect of the material type and the lubricant on the abrasive wear behaviour of two important commercially available ceramic on ceramic prosthetic systems, namely, Biolox^® forte and Biolox^® delta (CeramTec AG, Germany). A standard microabrasion wear apparatus was used to produce ‘3-body’ abrasive wear scars with three different lubricants: ultrapure water, 25 vol% new-born calf serum solution and 1 wt% carboxymethyl cellulose sodium salt (CMC-Na) solution. 1 μm alumina particles were used as the abrasive. The morphology of the wear scar was examined in detail using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Subsurface damage accumulation was investigated by Focused Ion Beam (FIB) cross-sectional milling and Transmission Electron Microscopy (TEM). The effect of the lubricant on the ‘3-body’ abrasive wear mechanisms is discussed and the effect of material properties compared.     

机械振动辅助激光熔覆Fe-Cr-Si-B-C涂层的显微组织及界面分布形态

采用机械振动辅助激光熔覆复合改性新工艺,在45钢表面制备了单道Fe-Cr-Si-B-C合金涂层。借助X射线衍射(XRD)、扫描电镜(SEM)和能量分散谱(EDS)分析了熔覆层的物相组成、微观结构和元素分布,通过HVS-1000型显微硬度计测试了熔覆层的显微硬度。结果表明,熔覆层主要由α-(Fe,Cr)固溶体、M7C3(M=Fe、Cr)碳化物、Fe2B硼化物和少量Fe0.9Si0.1组成。在机械振动辅助作用下,熔覆层结合界面组织由平面晶向带状和柱状晶转变,振幅为0.13~0.18mm时的晶粒细化效果最为明显;熔覆层中增强相形态随着频率的增加由短杆状向颗粒状、层状、条状转变,分布形态由杂乱分布向弥散分布和网状分布转变。相比未加机械振动的熔覆层,机械振动下的熔覆层中气孔、裂纹减少,显微硬度提高了约13.9%。这些结果显示熔覆层中显微组织形态及其分布主要受振幅和频率协同作用的影响。     

Book Reviews

Book reviewed in this article: Modern Physical Techniques in Materials Technology . Ed. by T. Mulvey and R. K. Webster . Electron Microscopy of Enzymes. Principles and Methods . Ed. by M. A. Hayat . The Principles and Techniques of Scanning Electron Microscopy: Biological Applications . Ed. by M. A. Hayat . Practical Methods in Electron Microscopy, Volume 2, Principles and Practice of Electron Microscopy Operation . Ed. by Audrey M. Glauert .