Rolling textures in nanoscale Cu/Nb multilayers

Rolling textures in nanoscale multilayered thin films are found to differ markedly from textures observed in bulk materials. Multilayered thin films consisting of alternating Cu and Nb layers with columnar grains were produced by magnetron sputtering, with individual layer thickness ranging from 4 μm to 75 nm and Cu/Nb interfaces locally satisfying the Kurdjumov–Sachs (K–S) orientation relations. After rolling to 80% effective strain, samples with a larger initial layer thickness develop a bulk rolling texture while those with a smaller initial layer thickness display co-rotation of Cu and Nb columnar grains about the interface normal, in order to preserve the K–S orientation relations. The resulting K–S texture has 0 0 1Nb parallel to and 1 1 0Cu approximately 5° from the rolling direction. A crystal plasticity model based on the Principle of Minimum Shear captures the K–S texture approximately and suggests that Nb drags Cu along in the rotation process.     

微/纳米尺度构件力学性能测试技术研究

微纳米尺度构件作为微纳米机电系统的重要组成部分,其力学性能是设计、制造微纳米机电系统的重要参数,对微纳米机电系统的使用性能、可靠性、服役寿命等均会产生显著的影响.由于受到量子效应、尺度效应、表面效应的影响,传统的测试技术已无法满足需要.结合国内外微纳米尺度构件力学性能测试的最新动态,介绍了纳米压入法、鼓泡法、微拉伸法、微梁弯曲法等测试方法的机理、应用及存在的主要问题.最后指出了微尺度力学性能测试的发展方向.     

Mechanical and corrosion properties of dc magnetron sputtered Al/Cr multilayers

Mechanical and corrosion properties of Al/Cr multilayer coatings deposited by dc magnetron sputtering are investigated and compared to pure Al and Cr coatings. The objective of this study is to increase the mechanical properties of sacrificial Al-based coatings. The results indicate that mechanical and corrosion properties depend on the architecture organisation. The reduction of the layer thickness allows an increase of the coating hardness. The nanolayer architecture leads to a “hard and tough” material compared to the other architectures. Moreover, the intrinsic corrosion resistance is enhanced, as the corrosion and the pitting corrosion potentials are progressively shifted towards positive values. The nanolayer coating presents the highest intrinsic corrosion resistance but multilayer and nanolayer Al/Cr coatings become nobler than the steel substrate. The corrosion resistance of the coated steel is then strongly dependent on the microscopic coating defects which act as preferential pathways for the corrosive solution. So the nanolayer architecture organisation improves the mechanical properties but does not permit to conserve the sacrificial behaviour of the aluminium based coating, which is harmful for the corrosion protection of coated steel.     

Oxygen-penetration-induced large hardness enhancement in nanoscale Nb/Ti multilayers

Nb/Ti multilayers with different modulation periods were prepared by magnetron sputtering deposition. Microstructure and mechanical properties were investigated by XRD, SEM and Nanoindentation. It turns out that hardness of samples increases with decreasing modulation wavelength (Λ) and then dropped at small Λ. Through scrutinizing other results in literature, we found that the coherent stress rather than modulus mismatch played more important role for hardness enhancement with decreasing Λ of the bcc-hcp multilayers. Annealing of samples in low (or high) vacuum at 400 C for 30 min led to large (or medium) enhancement of hardness, while the modulated structure was still maintained. It was found that annealing in low vacuum resulted in oxygen penetration into the multilayers as revealed by auger electron spectroscopy, but hardly changed metallic sheet resistivity. XRD results suggested that some niobium oxides were formed in Nb layers and oxygen distributed interstitially in Ti layers. The large hardness enhancement after annealing is mainly due to the strengthening effect from dispersive distribution of nano-scale niobium oxides and interstitial oxygen in the multilayers. In addition, interfaces between adjacent layers were more distinct after annealing which indicated good thermal stability of laminated structure.     

Mechanical and tribological properties of CrN/Ag and CrSiN/Ag nanoscale multilayers

This paper presents a concept of combining hard CrN (or CrSiN) and soft Ag lubricating materials in a nanoscale multilayer structure. The CrN/Ag and CrSiN/Ag multilayers are synthesized by reactive direct current (DC) magnetron sputtering techniques. The thickness of the Ag nanolayer in the multilayers is fixed to 4 nm while that of CrN and CrSiN nanolayers vary from 4 to 20 nm. The nitride layer effects on the mechanical and tribological properties of the multilayers have been investigated. Different mechanisms of the adhesion failure have been observed on the multilayer surfaces, depending on the nitride nanolayer types and their thicknesses. The CrSiN/Ag films exhibit poor adhesion whereas CrN/Ag multilayers demonstrate very good adhesion to AISI M2 steel substrates. The study of friction behaviors of the CrN/Ag multilayers against 100Cr6 steel balls reveals that the multilayers have low friction coefficients in comparison with that of a CrN single layer. The decrease of friction coefficients is related to the presence of the solid lubricant (Ag) nanolayer in the coatings.     

Cu/Nb纳米多层膜延性及其断裂行为

通过单轴拉伸试验研究恒定调制周期的聚酰亚胺基体Cu/Nb纳米金属多层膜的延性对调制比的依赖性,并采用聚焦离子束／扫描电子显微镜(FIB/SEM)截面定量表征技术深入分析多层膜的异质约束效应对断裂行为的影响.结果表明随着调制比的增加,多层膜的延性单调减小,出现由剪切型向张开型断裂模式的转变.当调制比小于某一临界值时,调制周期越小,多层膜延性越高;反之,则多层膜延性越差.这是由于软相Cu层对脆相Nb层中萌生的微裂纹扩展的约束作用.     

Characterization of EB-PVD yttrium-stabilised zirconia by nanoindentation

Nanoindentation was used to determine room temperature Young's modulus and hardness of the top surface and cross section of an electron beam physical vapor deposited yttrium-stabilized zirconia layer. In situ observations of indentations inside a scanning electron microscope (SEM) chamber were used along with normalized cross correlation (NCC) to evaluate the degree to which indentation of a columnar microstructure can be affected by elastic structural deformation. It was found that (i) the top surface Young's modulus is roughly twice that of the cross section. (ii) Upon isothermal heat treatment at 1100 °C for 80 h, an increase in Young's modulus and hardness occurred, to a greater degree in the bottom 20 μm of the cross section, and in the top surface, which was attributed to preferential sintering in these zones. (iii) NCC analysis of SEM observations of nanoindentation in the cross section gave an estimate of the extent to which elastic structural deformation is a constituent of the measured displacement. It was found that depending on the indenter location relative to the columnar microstructure, an underestimation of the Young's modulus by as much as a factor of four can occur.     

Mechanical response of amorphous ZrCuTi/PdCuSi nanolaminates under nanoindentation

In this paper, the relationship between mechanical response and shear band evolution for ZrCuTi (ZCT)/PdCuSi (PCS) nanolaminates under nanoindentation is discussed. Comparing to the monolithic amorphous ZCT and PCS films, the ZCT/PCS nanolaminates exhibit enhanced hardness and a more homogenous deformation mode. Cross-sectional transmission electron microscopy observations show that the shear-band patterns beneath the indent in ZCT/PCS nanolaminates are irregular and convoluted, and appear to be a mixture of the semi-circular shear bands and radial shear bands.     

基于纳米压痕法Sn3.0Ag0.5Cu焊点金属间化合物力学性能及其应变率效应的研究

采用纳米压入测试系统对无铅焊点Sn3.0Ag0.5Cu内金属间化合物(IMCs)Cu3Sn、Cu6Sn5的力学性能进行测试,应变率分别为0.01 s-1,0.05s-1,0.25s-1,0.5s-1,分析IMCs力学性能的应变率效应。研究发现金属间化合物具有应变率强化效应;Cu3Sn和Cu6Sn5的变形机制不同,前者加载曲线呈现锯齿流变,后者曲线光滑;Cu3Sn和Cu6Sn5的接触刚度在不同应变率时均与压痕深度成线性正比例关系;Cu3Sn的弹性模量和硬度明显高于Cu6Sn5;Cu3Sn和Cu6Sn5的硬度值均随着应变率的增大而增大,而对弹性模量没有明显影响。保载阶段,蠕变位移具有应变率强化效应,加载应变率为0.05s-1时做对比实验,Cu焊盘、Cu3Sn、Cu6Sn5和焊点的蠕变应变率敏感指数m分别为0.01627、0.0117、0.0184和0.0661。     

Structural transition and magnetic properties of evaporated Fe/Gd multilayers

Fe/Gd multilayers were prepared by alternate vapor deposition of pure Fe and Gd at a rate of 0.01-0.03 nm/s in an ultra-high-vacuum electron-gun evaporation system.The effects of the constituent metal layer thickness on the microstructures and magnetic properties of the films were investigated by low angle X-ray diffraction,transmission electron microscopy,and vibrating sample magnetometer.The experimental results show that a transition from the polycrystalline to amorphous state in the Fe layers occurs with the decrease of Fe layer thickness in the Fe/Gd multilayers.The saturation magnetization of the muitilayers reduces significantly with decreasing Fe layer thickness and increasing Gd layer thickness.A superparamagnetic behavior at room temperature is observed for the [Fe(0.6 nm)/Gd(4.0 nm)]15 multilayer due to the formation of discontinuous Fe layers.     

Thickness effect on interdiffusion of Fe/Pt multilayers

The effect of thickness on interdiffusion in Fe/Pt multilayer thin films was studied using rapid thermal annealing. [Fe(1 nm)/Pt(1 nm)]₂₀ and [Fe(3 nm)/Pt(3 nm)]₁₀ multilayers were prepared via DC magnetron sputtering and subsequently annealed at temperatures of 523 K to 603 K in an argon atmosphere in an infrared lamp furnace for a very short time. X-ray diffraction yielded the interdiffusion coefficients from the slopes of the satellite peak versus annealing time. The temperature dependence of interdiffusion in the range of 523 K to 603 K can be described by D(t)=3.42×10⁻¹⁵ exp(−0.83 eV/k_BT) (m²/s) for [Fe(1 nm)/Pt(1 nm)]₂₀ and D(t) =7.85×10⁻¹⁶ exp(−0.62 eV/k_BT) (m²/s) for [Fe(3 nm)/Pt(3 nm)]₁₀. The activation energy Q=0.83 eV for [Fe(1 nm)/Pt(1 nm)]₂₀ is higher than that of Q=0.62 eV for [Fe(3 nm)/Pt(3 nm)]₁₀. This phenomenon suggests that the atoms in the thicker film can move more easily in the interface and the lattice, which results in lower activation energy and higher diffusivity.     

Mechanical and tribological properties of TiN/Ti multilayer coating

A large area filtered arc deposition (LAFAD) technique was used to deposit TiN/Ti multilayer coatings with fixed TiN layer thickness and different Ti layer thickness. Nanoindention and pin-on-disk tribometer were used to characterize the hardness, elastic modulus, plasticity, friction coefficient, and wear rate of the multilayer coatings. The dependence of the mechanical and tribological properties of the coating on the Ti interlayer thickness was systematically studied. It was found that the increase in the Ti layer thickness resulted in a decrease in the effective hardness and elastic modulus, and an increase in the wear rate, plasticity, and toughness. The coatings with a Ti layer thicknesses of 0, 25 nm and 50 nm possess an excellent combination of high effective hardness (> 20 GPa), high plasticity (> 69%), low friction coefficient, and high wear resistance.     

The tribological behavior of spin-assisted layer-by-layer assembled Cu nanoparticles-doped hydrophobic polyelectrolyte multilayers modified with fluoroalkylsilane

Hydrophobic polyelectrolyte multilayers (PEMs) doped with Cu nanoparticles and modified with fluoroalkylsilane were prepared by a series of reaction cycles which consist of cycling the PEMs-coated substrate in Cu²⁺ and NaBH₄ solutions, where the polyelectrolyte multilayers were constructed by alternate pipetting of the solutions of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrene sulfonate) onto a spinning substrate. The as-prepared hydrophobic surfaces were characterized by means of X-ray photoelectron spectroscopy, atomic force microscopy, and contact angle measurement. The micro-friction and macro-tribological behavior of the multilayers were investigated. Results indicate that the micro-tribological behavior of the PEMs obeys the modified Amonton's Law, and the macro-tribological behavior of the Cu nanoparticles-doped hydrophobic PEMs is closely related to the wettability. Namely, the more hydrophobic the surfaces are, the longer the antiwear life is. Furthermore, the hydrophobic surfaces have lower friction coefficient under water lubrication than under dry-sliding. The reason lies in that the hydrophobic PEMs have low surface energy and less energy loss during sliding under water lubrication, leading to a lower friction coefficient.     

Nanoindentation analysis of the mechanical behavior of Zr-based metallic glasses with Sn, Ta and W additions

Zr₅₇Cu₂₀Al₁₀Ti₈Ni₅ and modified composition by adding Sn, W or Ta are studied using standard mechanical test and nanoindentation. Addition of refractory elements with a Sn micro-addition increases clearly the Young's modulus and the hardness of basic BMG. However, Sn reduces plasticity. Moreover these experiments allowed, in confine plasticity conditions, estimating an apparent activation volume associated to a plastic deformation (≈150 Å³).     

Length scale-dependent deformation behavior of nanolayered Cu/Zr micropillars

The mechanical behavior of incoherent Cu/Zr multilayers was studied in uniaxial compression experiments using micropillars with individual layer thicknesses (h) ranging from 5 to 100 nm. The deformation behavior of these micropillars are size dependent, transiting from dislocation dominated symmetrical slip at large h to shear localization induced by asymmetric slip and grain boundary mediated deformation at small h. During compression studies the multilayer micropillars exhibit a transition from strain hardening to shear softening at small h, and work softening at greater h. A maximum strain hardening rate is observed at a critical h of 20 nm, which was explained in terms of a transition from dislocation interactions to cross-slip of dislocations. The mechanical strength of the micropillars is also dependent on h, which was quantitatively analyzed using the confined layer slip model. In addition, the influence of pillar diameter on the mechanical behavior is also investigated. The effect of extrinsic size on the deformation mechanisms is discussed with respect to the intrinsic size effect with variation in h.     

反应溅射TiO/AlO和TiN/AlN薄膜的微结构与力学性能

采用Ti-Al镶嵌复合靶在Ar、N2和O2混合气体中反应溅射制备了一系列TiO/AlO和TiN/AlN薄膜,并采用EDS、XRD、TEM、AFM、SEM和微力学探针研究了薄膜的化学成分、微结构和力学性能.结果表明,随氧分压的提高,TiO/AlO和TiN/AlN薄膜中的氧含量逐步增加,氮含量相应减少,但其(Ti Al):(O N)仍保持约为1:1的化学计量比.薄膜保持与(Ti,Al)N薄膜相同的NaCl结构,并形成强烈(200)织构的柱状晶.与此同时,TiO/AlO和TiN/AlN薄膜的硬度和弹性模量也仍保持在与TiN/AlN薄膜相当的35GPa和370～420GPa的高值.由于薄膜中形成了相当含量的氧化物,这类薄膜的抗氧化能力有望得到提高.     

Fabrication, microstructure and tribological behavior of pulsed laser deposited a-CNx/TiN multilayer films

a-CN_x/TiN multilayer films were deposited onto high-speed steel substrates by pulsed laser ablation of graphite and Ti target alternately in nitrogen gas. The composition, morphology and microstructure of the films were characterized by energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The tribological properties of the films in humid air were investigated using a ball-on-disk tribometer. The multilayer films consist of crystalline TiN, metallic Ti and amorphous CN_x (a-CN_x). With an increase in thickness ratio of CN_x to bilayer, the hardness of multilayer film decreases, friction coefficient decreases from 0.26 to 0.135, and wear rate increases. The film with thickness ratio of CN_x to bilayer of 0.47 exhibits a maximum hardness of 30 GPa and excellent wear rate of 2.5 × 10^− 7 mm³ N^− 1 m^− 1. The formation of tribo-layer was observed at contact area of Si₃N₄ ball. The film undergoes the combined wear mechanism of abrasion wear and adhesion wear.