考虑相界效应的Ni基单晶合金纳米压痕模拟

利用分子动力学方法分别模拟金刚石压头压入Ni模型和Ni基单晶合金γ/γ′模型的纳米压痕过程,通过计算得到两种模型[001]晶向的弹性模量及硬度.采用中心对称参数分析不同压入深度时两种模型内部位错形核、长大过程以及Ni基单晶合金γ/γ′(001)相界面错配位错对纳米压痕过程的影响.结果显示:压入深度0.641 nm之前,两种模型的压入载荷-压入深度曲线相似,说明此时相界面处的错配位错对纳米压痕过程的影响很小;压入深度0.995 nm时,在错配位错处发生位错形核,晶体在γ相中沿着{111}面滑移,随即导致Ni基单晶合金γ/γ′模型压入载荷的下降,并在压入深度达到1.487 nm之前低于Ni模型相同压入深度时的压入载荷;压入深度从1.307 nm开始,由于相界面错配位错的阻碍作用,Ni基单晶合金γ/γ′模型压入载荷上升速度较快.     

Li2O-Al2O3-SiO2微晶玻璃加工脆延转变临界条件实验研究

 介绍了Li2O-Al2O3-SiO2微晶玻璃的加工特点。基于纳米划痕技术对Li2O-Al2O3-SiO2微晶玻璃进行了纳米划痕实验,测得微晶玻璃材料脆延转变临界切削深度和临界载荷的平均值分别为125.6 nm和29.78 mN。将实验所得临界切削深度值与基于压痕断裂力学模型建立的脆延转变临界切削深度计算值进行了对比,结果表明,T. G. Bifano基于显微压痕法给出的临界切削深度计算值与实验结果差别较大,结合实验结果对其公式进行了修正;基于压痕断裂力学模型建立的延性域磨削临界切削深度计算值与实验结果相差较小,并分析了产生差异的原因。     

初始压入位置对Ni基单晶合金纳米压痕影响研究

针对Ni基单晶合金建立初始压入γ 相的γ /γ' 模型和初始压入γ'相的γ'/γ 模型, 采用分子动力学方法模拟金刚石压头压入两种模型的纳米压痕过程, 计算两种模型[001]晶向硬度. 采用中心对称参数分析两种模型(001)相界面错配位错对纳米压痕过程的影响. 结果显示: 弛豫后, 两种模型(001)相界面错配位错形式不同, 其中γ'/γ 模型(001)相界面错配位错以面角位错形式存在; 压入深度在0.930 nm 之前, 两种模型(001)相界面错配位错变化不大, 压入载荷-压入深度及硬度-压入深度曲线较符合; 压入深度在0.930 nm之后, γ'/γ 模型(001)相界面错配位错长大很多, 导致相同压入深度时γ'/γ 模型比γ /γ'模型压入载荷和硬度计算结果小; 压入深度在2.055 nm之后, γ /γ'模型(001)相界面错配位错对γ 相中位错进入γ'相有阻碍作用, 但仍有部分位错越过(001) 相界面进入γ' 相中, γ'/γ 模型(001)相界面处面角位错对γ' 相中位错进入γ 相有更明显的阻碍作用, 几乎无位错越过(001) 相界面进入γ 相中, 面角位错的强化作用更明显, 所以γ'/γ 模型比γ /γ'模型压入载荷上升速度快.     

溅射压强对TiN/SiNx纳米多层膜微观结构及力学性能的影响

利用磁控溅射方法在不同溅射压强条件下制备了TiN/SiN_x纳米多层膜.多层膜的微观结构及力学性能分别用X射线衍射仪、原子力显微镜及纳米压痕仪来表征.结果表明随着溅射压强的增大,多层膜的界面变模糊,TiN层的择优取向由(200)晶面过渡到(111)晶面.与此同时,多层膜的表面粗糙度增大,硬度和弹性模量随溅射压强的增大而减小.多层膜力学性能的差异主要是由于薄膜的周期性结构及致密度存在差异所致. 关键词： x多层膜')" href="#">TiN/SiN_x多层膜 界面宽度 表面形貌     

纳米压痕条件下 MgB2 超导块材的压入力学行为研究

本文采用纳米压痕技术对固相烧结法制备的 MgB2 超导块材进行压入力学实验, 对不同压深的载荷-位移曲线和纳米压痕数据的再现性进行了分析, 实验数据使用 Oliver-Pharr 方法计算得出 MgB2 的硬度值, 借助经验方程拟合纳米压痕蠕变曲线求得蠕变速率敏感指数(m ) . 结果表明, 微观结构不均匀性会对材料在压头压入过程中抵抗外力作用时产生影响, 使压痕数据再现性变差; MgB2 的硬度表现出尺寸效应, 即随着压入深度的增加硬度逐渐下降;m 值随压入深度增加而增加是位错滑移速度加快的结果.     

反应等离子喷涂纳米TiN涂层的显微硬度及微观结构研究

阐述了反应等离子喷涂(RPS)方法的基本思想.利用气体隧道等离子喷枪，通过RPS方法在Q23 5钢基底上成功制备了氮化钛涂层.检测了TiN涂层在不同载荷下的显微硬度，结果显示TiN涂层具有明显的硬度压痕尺寸效应，在高载荷下加工硬化效应较弱.XRD,TEM及HRTEM等分析 表明,通过RPS方法制备得到了纳米TiN涂层，涂层由直径约为50—70nm的TiN晶粒及非晶Ti N所组成. 关键词： 反应等离子喷涂 纳米 氮化钛 微观结构     

界面和择优取向对TiN/ZrN纳米多层膜硬度变化的影响

利用射频反应磁控溅射方法，制备了调制比约为4，调制周期不同的一系列TiN/ZrN纳米多层膜. 利用X射线衍射仪(XRD)、高分辨电子显微镜(HRTEM)和纳米压痕仪(Nanoindentation)对多层膜的调制结构、界面状态和力学性能进行了表征. 研究结果表明TiN/ZrN多层膜具有很好的调制结构，但是在TiN层和ZrN层之间存在一定厚度的界面混合层. 力学性能分析表明：当调制周期小于15 nm时，TiN/ZrN多层膜的硬度介于单一TiN和ZrN薄膜的硬度之间；当调制周期为15.24 nm时，硬度达到最大，但随着调制周期增加，多层膜的硬度基本上保持为常数. 分析了TiN/ZrN多层膜硬度变化的机制，认为界面厚度和择优取向是导致硬度变化的主要原因. 关键词： TiN/ZrN多层膜 界面宽度 择优取向 硬度变化     

TiN和Ti1-xSixNy薄膜的微观结构分析

使用x射线衍射(XRD)、x射线光电子谱(XPS)、高分辨透射电子显微镜(HRTEM)和原子力显微镜(AFM)多种观测手段分析了TiN薄膜和Ti1-xSixNy纳米复合薄膜的微观结构.实验分析证明Ti1-xSixNy薄膜是由直径为3-5nm的纳米晶TiN和非晶Si3N4相构成,并且Ti1-xSixNy薄膜的表面粗糙度小于相同条件下制备的TiN薄膜,在Ti1-xSixNy薄膜体系的自由能中引入界面能的概念,在此基础上分析了体系中TiN晶粒的取向问题.     

TaN/TiN和NbN/TiN纳米结构多层膜超硬效应及超硬机理研究

采用射频磁控溅射方法制备单层TaN,NbN和TiN薄膜和不同调制周期的TaN/TiN和NbN/TiN纳米多层膜.薄膜采用X射线衍射仪、高分辨率透射电子显微镜和显微硬度仪进行表征.结果表明TaN/TiN和NbN/TiN纳米多层膜在一定的调制周期范围内均呈共格界面,相应地均出现了超硬效应,且最大硬度值接近.分析了TaN/TiN与NbN/TiN纳米多层膜的超硬机理,TaN/TiN的晶格错配度与NbN/TiN的接近,但TaN/TiN的弹性模量差与NbN/TiN的有一定的差别,表明由于晶格错配使共格外延生长在界面处 关键词： TaN/TiN纳米多层膜 NbN/TiN纳米多层膜 外延生长 超硬效应     

纳米压痕法测量Cu的室温蠕变速率敏感指数

把恒加载速率/载荷法（const.P·/P）和恒载荷法（const.P）相结合，提出了一个稳态加载和长时间保载的纳米压痕蠕变试验新方法.该方法不仅适用于高蠕变能力的低熔点材料，也适用于低蠕变能力和存在压痕尺寸效应的高熔点材料.用该方法确定Cu的室温蠕变速率敏感指数m为0.01，并发现其值不受加载段所用的P·/P值和达到的最大压入位移h-max的影响. 关键词： 纳米压痕 铜 蠕变 蠕变速率敏感指数     

Deformation and fracture of TiN coating on a Si(1 1 1) substrate during nanoindentation

The deformation mechanisms and fracture behavior of TiN coating on a Si(111) substrate, deposited using magnetron sputtering Ti target, is characterized by nanoindentation experiments. The morphologies of the indentations are revealed by scanning electron microscopy, coupled with in situ atomic force microscopy in nanoindentation experiments. The results show that permanent trigonal impressions and radial plastic grooves are confined within the contact regions even though the peak indenter displacement increases to 1500 nm. Local cracks of TiN appear around the indent marks making the edges of the indentations irregular. The cracks increase with an increase of the indenter displacement until the indenter arrives at (or approaches) the Si(1 1 1) substrate at a critical displacement. As the peak indenter displacement increases to 2500 nm, an interfacial fracture between the TiN coating and the Si(1 1 1) substrate is observed using both scanning electron microscopy micrograph and in situ atomic force microscopy images. The diameter of the interfacial fracture determined by scanning electron microscopy micrographs is more accurate than that determined by in situ atomic force microscopy images in nanoindentation experiments. The failure mechanism of the TiN coating is also investigated by means of a standard nanoscratch test.     

Indentation fracture and indentation delamination in ZnO film/Si substrate systems

ZnO films with thicknesses ranging from 0.202 to 1.535?µm were deposited by using the magnetron sputtering technique on Si (100) substrates 525?µm thick. Then, Vickers indentation tests were carried out on the ZnO/Si systems at room temperature, in which the applied load varied from 10?mN to 2.0?N. The experimental results show that only indentation-induced radial cracking occurred in the systems with film thicknesses equal to and thinner than 0.554?µm, from which the residual stress in the films was extracted to be 387?MPa in compression. For the systems with film thicknesses equal to and thicker than 0.832?µm, only indentation-induced delamination occurred when indentation loads were low. Under high indentation loads, radial cracking concurrently occurred with delamination. The radial cracks were invisible at the film surfaces because the crack length was smaller than the delamination size. The critical film thickness for indentation-induced delamination was found to be around 0.7?µm for the ZnO/Si systems. Combining the composite hardness models with the indentation-induced delamination model, we developed a method to determine the interfacial fracture energy between a film and its substrate. The novel method is particularly useful for indentation equipment without any displacement measurement devices. Using the new method, we extracted the interfacial fracture energy to be about 12.2?J?m^?2 and from 9.2 to 11.7?J?m^?2 for the cases without and with buckling respectively of delaminated films. Consequently, the pure mode I interfacial fracture energy was calculated to be 10.4?J?m^?2 for the ZnO/Si systems.     

Phase transformation of Ni/Si thin films induced by nanoindentation and annealing

Thin Ni/Si films are prepared by depositing a Ni layer with a thickness of 100 nm on a Si (100) substrate. The as-deposited thin-film specimens are indented to a maximum depth of 500 nm using a nanoindentation technique and are then annealed at temperatures of 200°C, 300°C, 500°C and 800°C for 2 min. The microstructural changes and phases induced in the various specimens are observed using transmission electron microscopy (TEM) and micro-Raman scattering spectroscopy (RSS). Based on the load-displacement data obtained in the nanoindentation tests, the hardness and Young’s modulus of the as-deposited specimens are found to be 13 GPa and 177 GPa, respectively. The microstructural observations reveal that the nanoindentation process prompts the transformation of the indentation-affected zone of the silicon substrate from a diamond cubic structure to a mixed structure comprising amorphous phase and metastable Si III and Si XII phases. Following annealing at temperatures of 200∼500°C, the indented zone contains either a mixture of amorphous phase and Si III and Si XII phases, or Si III and Si XII phases only, depending on the annealing temperature. In addition, the annealing process prompts the formation of nickel silicide phases at the Ni/Si interface or within the indentation zone. The composition of these phases depends on the annealing temperature. Specifically, Ni₂Si is formed at a temperature of 200°C, NiSi is formed at a temperature of 300°C and 500°C, and NiSi₂ is formed at 800°C.     

Numerical simulation of micro-scratch tests for coating/substrate composites

In this paper the micro-scratch test is simulated by ANSYS finite element code for thin hard coating on substrate composite material system. Coulomb friction between indenter and material surface is considered. The material elastic-plastic properties are taken into account. Contact elements are used to simulate the frictional contact between indenter and material surfaces, as well as the frictional contact after the detachment of coating/substrate interfaces has taken place. In the case of coating/substrate interfaces being perfectly bonded, the distributions of interfacial normal stress and shear stress are obtained for the material system subjected to normal and tangential loading. In the case of considering the detachment of interfaces, the length of interfacial detachment and the redistribution of stresses because of interfacial detachments are obtained. The influences of different frictional coefficients and different indenter moving distances on the distributions of stresses and displacements are studied. In the simulation, the interfacial adhesion shear strength is considered as a main adhesion parameter of coating/substrate interfaces. The critical normal loading from scratch tests are directly related to interfacial adhesion shear strengths. Using the critical normal loading known from experiments, the interfacial adhesion shear strength is obtained from the calculation. When the interfacial adhesion shear strength is known, the critical normal loading is obtained for different coating thicknesses. The numerical results are compared with the experimental values for composite materials of thin TiN coating on stainless steel substrate.     

Pulsed KrF laser deposited GaN/TiN/Si(111) heterostructures by sequential TiN and liquid Ga laser ablation

GaN/TiN heterostructures were deposited on 4° miscut Si(111) substrates by pulsed KrF laser ablation of TiN through vacuum, followed by reactive pulsed KrF laser ablation of liquid Ga through 70-75 mTorr of microwave-activated NH₃. Deposition temperatures of 950 °C and 1050 °C were employed for the TiN layer while 900 °C was employed for the GaN layer. The targets were positioned 5 cm from the substrate and ablated by using a reimaging beamline at a nominal energy density of 3-4 J/cm². X-ray diffraction (XRD) revealed a highly textured heterostructure with GaN(0001)//TiN(111)//Si(111) and with a rocking curve width for both GaN(0001) and TiN(111) equal to ~1.1°. The mosaic spread through the TiN(001) reflection was ~1.3°, whereas that of the GaN(101_1) was undetectable because of low S/N. Scanning electron microscopy revealed large oriented 10 7m-sized hexagonal crystallites decorating large depressions in the TiN film with many smaller pits also present. The effect of substrate processing and TiN film processing on pit formation was explored.     

Microstructure, mechanical properties, and oxidation resistance of nanocomposite Ti-Si-N coatings

Ti-Si-N coatings with different silicon contents (0-12 at.%) were deposited onto Si(1 0 0) wafer, AISI M42 high speed steel, and stainless steel plate, respectively. These coatings were characterized and analyzed by using a variety of analytical techniques, such as XRD, AES, SEM, XPS, nanoindentation measurements, Rockwell C-type indentation tester, and scratch tester. The results revealed that the hardness was strongly correlated to the amount of silicon addition into a growing TiN film. The maximum hardness of 47.1 GPa was achieved as the Si content was 8.6 at.%. In the mechanical and oxidation resistance measurements, the Ti-Si-N coatings showed three distinct behaviors. (i) The coatings with Si contents of no more than 8.6 at.% performed good adhesion strength quality onto the HSS substrates. (ii) The fracture toughness of the coatings decreased with the increase in Si content. (iii) The Ti-Si-N coating with 8.6 at.% Si showed the excellent oxidation resistance behavior. The cutting performance under using coolant conditions was also evaluated by a conventional drilling machine. The drills with Ti-Si-N coatings performed much better than the drills with TiN coating and the uncoated drills.     

Effect of pulsed bias on properties of ZrN/TiZrN films deposited by cathodic vacuum arc

ZrN/TiZrN multilayer are deposited by cathodic vacuum arc method with different substrate bias (from 0 to -800 V), using Ti and Zr plasma flows in residual N₂ atmosphere, combined with ion bombardment of sample surfaces. The effect of pulsed bias on structure and properties of films is investigated. Microstructure of the coating is analyzed by X-ray diffraction (XRD), and scanning electron microscopy (SEM). Meanwhile, the nanohardness, Young's modulus, and scratch tests are performed. The experimental results show that the films exhibit a nanoscale multilayer structure consisting of TiZrN and ZrN phases. Solid solutions are formed for component TiZrN films. The dominant preferred orientation of TiZrN films is (111) and (220). At pulsed bias of -200 V, the nanohardness and the adhesion strength of ZrN/TiZrN multilayer reach a maximum of 38 GPa, and 78 N, respectively. The ZrN/TiZrN multilayer demonstrates an enhanced nanohardness compared with binary TiN and ZrN films deposited under equivalent conditions.     

A transmission electron microscopy study of the deformation behavior underneath nanoindents in nanoscale Al–TiN multilayered composites

Nanoscale multilayered Al–TiN composites were deposited using the dc magnetron sputtering technique in two different layer thickness ratios, Al : TiN = 1 : 1 and Al : TiN = 9 : 1. The Al layer thickness varied from 2 nm to 450 nm. The hardness of the samples was tested by nanoindentation using a Berkovich tip. Cross-sectional transmission electron microscopy (TEM) was carried out on samples extracted with focused ion beam from below the nanoindents. The results of the hardness tests on the Al–TiN multilayers with two different thickness ratios are presented, together with observations from the cross-sectional TEM studies of the regions underneath the indents. These studies revealed remarkable strength in the multilayers, as well as some very interesting deformation behavior in the TiN layers at extremely small length scales, where the hard TiN layers undergo co-deformation with the Al layers.