Electrodeposition of Cu/Ni compositionally modulated multilayers by the dual-plating bath technique

Electrodeposition of Cu/Ni Compositionally Modulated Multilayers (CMM) has been attempted by the dual-plating bath technique. In a very simple set-up using a manual transfer of the substrate from one bath to another, multilayers with sublayer thicknesses of 100, 25 and 5 nm have been deposited. Cross-sectional scanning, transmission electron microscopy and X-ray texture measurements have been used to characterize the samples. A number of problems encountered in the deposition of a good quality CMM have been identified. The possibility of improving the quality of the layered structure through the selection of appropriate plating parameters has been demonstrated. It has been shown how the electrocrystallization of thin copper layers differs quite markedly from that of thin nickel layers.     

铜铝复合板的拉深变形行为

对轧制态及退火态铜铝复合板进行了室温拉伸试验,得到了其不同变形速度下的强度和塑性性能数据,计算了其不同变形速度下的应变硬化指数n值,以得到其优化的拉深速度.分别在无润滑、20号机油润滑以及聚丙烯薄膜润滑3种条件下对两种状态的铜铝复合板进行拉深试验,测量变形后的极限拱顶高度日,观察分析缺陷位置以及界面层演变规律.结果 表...     

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.     

基于大变形理论的塑性变形量线性递减矫直理论研究

由于H型钢具有诸多优点而在多个领域得到越来越广泛的应用,但其在生产过程中必须经过矫直工序。对基于大变形压弯矫直理论的塑性变形量线性递减矫直理论进行了研究,讨论了传统方法的局限性,并对九辊型钢矫直机矫直HW300×300 H型钢的矫直规程进行了实例计算,得到了更为精确的矫直规程制定方法。     

Microstructure and strengthening mechanisms in Cu/Fe multilayers

Nanostructured Cu/Fe multilayers on Si (1 1 0) and Si (1 0 0) substrates were prepared by magnetron sputtering, with individual layer thicknesses h varying from 0.75 to 200 nm. The growth orientation relationships between Cu and Fe at the interfaces were determined to be of the Kurdjumov–Sachs and Nishiyama–Wasserman type. Nanoscale columnar grains in Fe, with an average grain size of 11–23 nm, played a dominant role in the strengthening mechanism when h ? 50 nm. At smaller h the hardness of Cu/Fe multilayers with (1 0 0) texture approached a peak value, followed by softening due to the formation of fully coherent interfaces. However, abundant twins were observed in Cu/Fe films with (1 1 1) texture when h = 0.75 nm, which led to the retention of high hardness in the multilayers.     

Length-scale-dependent deformation and fracture behavior of Cu/X (X = Nb, Zr) multilayers: The constraining effects of the ductile phase on the brittle phase

The plastic deformation and fracture behavior of two different types of Cu/X (X = Nb, Zr) nanostructured multilayered films (NMFs) were systematically investigated over wide ranges of modulation period (λ) and modulation ratio (η, the ratio of X layer thickness to Cu layer thickness). It was found that both the ductility and fracture mode of the NMFs were predominantly related to the constraining effect of ductile Cu layers on microcrack-initiating X layers, which showed a significant length-scale dependence on λ and η. Experimental observations and theoretical analyses also revealed a transition in strengthening mechanism, from single dislocation slip in confined layers to a load-bearing effect, when the Cu layer thickness was reduced to below ∼15 nm by either decreasing λ or increasing η. This is due to the intense suppression of dislocation activities in the thin Cu layers, which causes a remarkable reduction in the deformability of the Cu layers. Concomitantly, the constraining effect of Cu layers on microcrack propagation is weakened, which can be used to explain the experimentally observed λ and η-dependent fracture mode transition from shear mode to an opening mode. Furthermore, the fracture toughness of the NMFs is also found to be sensitive to both λ and η. A fracture mechanism-based micromechanical model is developed to quantitatively assess the length-scale-dependent fracture toughness, and these calculations are in good agreement with experimental findings.     

低Ni/Cu比钢中铜的富集行为

采用热重分析仪和扫描电镜研究了不同加热温度和升温速率下Ni/Cu比为0.39的低Ni/Cu比含铜钢铜富集行为。研究结果表明:在1050～1300℃加热温度范围内,富集相以富Cu-Ni相和富Ni相为主,且以颗粒形式弥散分布于氧化皮内部或氧化皮与钢基体界面;除1250℃外,随加热温度升高,富集相中Ni/Cu比值逐渐增加,在1200℃和1300℃时,富集相仅为富Ni相。加热温度为1250℃时,升温速率不同,富集相的Ni/Cu比值和氧化皮与钢基体界面形态不同:采用5℃/min低速升温和15℃/min高速升温均有利于增加Ni/Cu比值,而采用10℃/min中速升温导致Ni/Cu比值偏低;增加升温速率,缩短加热时间,使氧化皮与钢基体界面更加平滑,有利于除鳞以改善钢材表面质量。对生产高表面质量低Ni/Cu比含铜钢而言,可采取低温加热或高温加热,将加热温度分别控制在1180～1220℃或者1280～1320℃;也可采用1220～1280℃中温加热,将弱氧化性气氛下分阶段步进梁加热炉的第三阶段升温速率控制在15℃/min左右。     

A new single bath for the electrodeposition of NiFe/Cu multilayers exhibiting giant magnetoresistance behavior

A new single bath for the electrodeposition of ultrathin NiFe/Cu multilayers was developed and magnetoresistance measurements were conducted. Complementary methods such as scanning electron microscopy (SEM), x-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the multilayers. Magnetoresistance measurements indicated that the multilayers grown from this new bath exhibited a giant magnetoresistance (GMR) behavior.     

Giant magnetoresistance and super-paramagnetism in electrodeposited NiFe/Cu multilayers

The giant magnetoresistance of electrodeposited NiFe/Cu multilayers from a single bath under potentiostatic control is studied. The observed nonsaturating behavior urged us to investigate the probability of the occurrence of superparamagnetic regions in these multilayers. In this research, for the first time, the presence of super-paramagnetic regions in electrodeposited NiFe/Cu multilayers is shown and proved via high resolution transmission electron microscopy. The reason was found to be the existence of a very large anodic transient at the beginning of the copper deposition pulse, which could be eliminated by choosing a more negative potential.     

Ti-50.1Ni形状记忆合金相变与形变行为

用热重分析仪、X射线衍射仪和拉伸试验研究了退火温度、变形温度对Ti-50.1Ni形状记忆(SME)合金丝的相变、形变的影响.Ti-50.1Ni合金加热氧化过程中温度超过600℃后氧化加剧,故退火温度不宜超过600℃.该合金奥氏体相变开始温度(As)高于室温,室温相为马氏体,呈SME特性.350～600℃退火态Ti-50.1Ni合金在室温下均呈SME.     

Sputter-deposited Cu/Cu(O) multilayers exhibiting enhanced strength and tunable modulus

By means of brief pauses in radiofrequency (RF) sputter deposition between individual layers, ultrathin copper oxide layers were formed through adsorption in the Cu/Cu multilayers. Their mechanical properties were compared with the Cu/Cu(O) multilayers whose oxide layers were deliberately deposited between copper layers. The mechanical hardness value of the Cu/Cu(O) multilayers approached that of nanostructured copper thin films. The Young’s modulus of the multilayers was tunable, in accordance with the elasticity theories of composites. In addition, the Hall–Petch slope of the RF sputter-deposited Cu monolayers indicated that their theoretical strength approached the shear modulus of copper.     

Thermal stability of microstructure and mechanical properties of Ni/Ru multilayers

The microstructure, hardness and thermal stability of Ni/Ru multilayers prepared by evaporation deposition were investigated by X-ray diffraction, transmission electron microscopy, vacuum annealing and nanoindenation. The hardness values of as deposited multilayers increase, while their elastic modulus values decrease, with decreasing periodicity. After annealing at low temperature (below 450 °C), the decrease in hardness of multilayers with larger periodicity is more remarkable than that of multilayers with smaller periodicity due to coarsening of the in-plane grain size. The higher temperature (600 °C) annealing results in the breakdown of the periodical structure and a significant drop in hardness for multilayers with smaller periodicity. The results were discussed according to Orowan-type single dislocation bowing mechanism.     

Electrodeposition of NiFe/Cu multilayers from a single bath

NiFe/Cu multilayers were deposited from a single bath in the potentiostatic mode using two different solutions. In solution A, the ionic concentration ratios were Fe²⁺: Ni²⁺: Cu²⁺ 9: 60: 10 and in solution B they were 1: 103: 1. To characterize the layers, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and atomic force microscopy (AFM) were used. SEM results revealed the layered structure of the deposits for relatively thick bilayers. While HRTEM provided direct evidence for the composition modulation across successive layers in the NiFe/Cu nanometer-multilayered structure prepared from solution B. Therefore, the layers prepared from solution B seemed to be more appropriate for giant magnetoresistance (GMR) applications. The effect of stirring during the electrodeposition process of the multilayers was also investigated.     

Cu对5052铝合金热拉伸变形行为的影响

利用Gleeble-3500热模拟试验机与透射电镜(TEM)研究了Cu对5052铝合金热拉伸变形行为的影响。研究表明:Cu的添加导致5052铝合金在等温拉伸温度为100℃、拉伸速率为0.01 mm·s-1与拉伸温度为250℃、拉伸速率为0.01 mm·s-1与0.1 mm·s-1的真应力-真应变曲线上出现由动态应变时效引起的锯齿波动,不同升温速率与拉伸速率组合下的非等温拉伸真应力-真应变曲线上出现由动态析出引起的屈服平台。     

退火对Co/Cu多层膜微观结构和磁性能的影响

研究了退火对磁控溅射Co/Cu多层膜微观结构和磁性能的影响。用扫描电子显微镜(SEM),透射电子显微镜(TEM)观察了沉积态及在不同温度退火后Co/Cu多层膜表面及截面的显微组织,用能谱仪(EDS)分析了退火后Co/Cu多层膜截面的元素分布,用综合物性测量系统(PPMS)对Co/Cu多层膜的磁滞回线进行了测量。表面显微组织的观察结果表明退火温度低于450℃时,多层膜表面形貌变化不大,均是由细小的晶粒组成。退火温度高于该温度后,随退火温度的升高,晶粒迅速长大。截面显微组织的观察结果和元素分布的测试结果表明,磁控溅射的Co/Cu多层膜内有大量柱状晶,随退火温度升高柱状晶长大。当退火温度达到600℃后,多层膜内的层状结构被破坏。磁滞回线的测量结果表明,退火温度低于400℃时,Co/Cu多层膜的磁性能变化不大,退火温度高于该温度后,随退火温度升高,矫顽力迅速增大。     

Evaluating modulus and hardness enhancement in evaporated Cu/W multilayers

The microstructure, hardness and elastic modulus of Cu/W multilayers prepared by evaporation deposition were investigated by X-ray diffraction, transmission electron microscopy and nanoindenation. The results show that the multilayers with good modulation structure have asymmetrical interfaces. The W on Cu interfaces are relatively sharp, while the Cu on W interfaces are diffuse, with significant intermixing. The intermixing results in compression of the out-of-plane interplanar spacing of the W layer. The compression increases with decreasing periodicity and leads to modulus enhancement. The hardness values also increase with decreasing periodicity, which is interpreted by the Lehoczky model.     

Microstructure and interface fracture of LPPS Ni／Fe and Cu／Ni sprayed materials

The interfaces of two materials, Ni/Fe and Cu/Ni, deposited by low pressure plasma spraying method,were studied by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDS). The adhesion between coatings and substrates was measured with the aid of Knoop interfacial indentation testing method. The results show that the interfacial micrcstructures have strong influence on the mechanical properties. Cu/Ni interface is weak link with NiO amorphousphase. Ni/Fehave strong in-interracial layer consists primarily of Fe and Ni oxide crystalline phases, containing dispersive (Fe, Ni) spotlike intermetaUic compound phase in nanometer dimension, and the interracial interdiffusion was detected. The micro-mechanism of interracial fracture was discussed.