Hard Chromium Plating of Large Cast Iron Drum-Drier Rolls

The principles of rinsing with recirculated water containing a small concentration of dissolved solids are examined, and equations are developed for single, multiple, and counterflow rinsing. Two theoretical viewpoints are taken; the complete mixing theory, which makes the most optimistic prediction for contaminant removal from the work surface, and the diffusion theory, which makes the most pessimistic prediction. An index of rinsing efficiency is proposed and various rinsing techniques are compared using it. A simple theory of the action of chemical rinses is developed, which suggests that these processes, originally adopted as a method of effluent treatment, can also increase rinsing efficiency.     

电沉积Ni-Mo和Ni-Mo-P合金的热力学分析

利用热力学数据计算并绘制了ＮｉＰＨ２Ｏ系电位—ｐＨ图,根据电位—ｐＨ图分析了电沉积ＮｉＭｏ和ＮｉＭｏＰ合金镀层的电化学行为;利用Ｘ射线衍射测试了ＮｉＭｏ和ＮｉＭｏＰ镀层在镀态下的物相组成。热力学分析表明：Ｍｏ和Ｐ都难以单金属的形式沉积,它们必须和其它金属以诱导共沉积的方式才能沉积出来;Ｐ,Ｎｉ能以金属间化合物Ｎｉ３Ｐ的形式在阴极上沉积;Ｍｏ以两种形式进入阴极,一种为以ＭｏＯ３固体颗粒复合电镀进入镀层,另一种为以金属间化合物的形态沉积。Ｘ射线衍射分析表明,Ｐ以Ｎｉ３Ｐ,Ｍｏ以ＭｏＯ３与ＭｏＣ的形式存在于镀层中,这一结果与热力学分析结论相一致。     

Electroless deposited ternary alloys: third element chemical state,localisation and influence on the properties. A short review

Electroless deposited ternary alloys have been reviewed in relation to the chemical state of the third element, its localisation and the possible influence of these on alloy properties. Three types of electroless Ni–W–P, Co–W–P and Ni–Zn–P coatings have been investigated. Low P deposits are nanocrystalline and those with higher P content are amorphous. X-ray diffraction has proved the localisation of W, Zn and P along the nanograin boundaries. The localisation of Zn along with P has also been confirmed by transmission electron microscopy combined with energy dispersion spectroscopy. Analysing the X-ray photoelectron spectroscopy (XPS) spectra it has been found that within the coatings W is in elemental form, whereas Zn is partially oxidised. XPS data also show that the crystalline structure promotes the surface oxidation to a higher extent than in the case of amorphous structure. The wear resistance of nanocrystalline Ni–W–P coatings is much higher. A lower corrosion resistance of amorphous Ni–W–P coatings has been found by weight-loss method during long-term immersion in 5% NaCl. It is illustrated that in addition to the composition and structure, the properties depend on the distribution and chemical state of the alloy components.     

应用电流表在线监控混砂机易损件的磨损

混砂机效率的发挥直接影响型砂性能。随着混砂机中各转子叶片的磨损,其混砂效率逐渐下降。为有效监控混砂机的易损件磨损,分析了影响转子混砂机效率的因素,介绍了使用电流表监控混砂机中各电机工作电流波动值的方法,从而准确判断混砂机易损件的磨损情况,避免原来监控方法的不足,有效发挥混砂机的工作效率。     

基于混色3D打印工艺的混料腔均匀性结构设计

目前,市面上多进一出的混色3D打印设备存在混色不均、色块交界域明显等问题。依据高熔融态聚物混合原理,提出一种利用耗材挤入混合腔体积反推混合腔尺寸的方法,并从结构、压力及速度分布等流场特性对混合腔结构进行分析。分析结果表明,耗材射入混合腔角度及喉管排列形式对混合效果有较大影响。试验结果表明:该方法不仅能够实现不同基色熔融态耗材均匀混合问题,而且能够提高混合效率、缩短混合时间,为混色3D打印提供一种可行的方法。     

化学镀Ni-Fe-P和Ni-Fe-P-B合金的耐蚀性研究

利用失重法和电化学测试法,对比研究以铝合金为基体化学镀Ni-Fe-P和Ni-Fe-P-B合金的耐蚀性.结果表明:这两种镀层浸泡在3.5%NaCl和10%NaOH溶液中均比浸泡在0.1mol/L H2SO4和1mol/L HCl中有更好的耐蚀性.另外,在3.5%NaCl和10%NaOH溶液中,Ni-Fe-P-B镀层合金比Ni-Fe-P有更好的耐蚀性;但是在0.1mol/L H2SO4和1mol/L HCl溶液中,Ni-Fe-P镀层合金却比Ni-Fe-P-B有更好的耐蚀性;     

Laser nanocrystallisation and corrosion behaviour of electroless Ni–W–P coating with high phosphorus content

This paper reports an investigation of microstructural characteristics in electroless Ni–3·9W–13·4P (wt.%) coating by laser nanocrystallisation using a quantitative X–ray diffraction (XRD) method and scanning electron microscopy (SEM) with energy dispersive X–ray spectroscopy (EDX). The corrosion resistance of the coatings before and after laser treatment has been evaluated in 0·5 M H₂SO₄ solution by potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) techniques. The results show that the laser treatment improves the corrosion resistance of the coatings. The corrosion mechanism has been studied and correlated to the microstructural characteristics including volume fraction of I_Ni3P/I_total, microstrain, and the crystallite size of the Ni and Ni₃P phases.     

基于主成分分析和变权相似性的粉体混合均匀性判断

为判断烧结型滚抛磨块制备过程中粉体原料的混合均匀性, 提出基于多图像相似性的粉体混合均匀度检测方法。 首先设计粉体采样装置在线采集粉体样本, 并利用数字显微镜采集粉体样本图像。 然后提取基于灰度直方图的图像灰度分布统计特征作为粉体图像特征参数, 采用主成分分析法(PCA)对特征参数降维, 并构建粉体图像特征矩阵。 最后计算每组图像中各粉体图像与样本密度中心的变权重相似度, 取其最小值作为该组图像的相似度, 并设定合适阈值判断粉体是否混合均匀。 试验结果表明: 该方法可以较为准确地判断混合终点, 并确定最佳混合时间, 适用于磨块粉体原料混合均匀性的判断, 从而提高生产效率和磨块质量, 提高经济效益。      

Brazing of UNS S32101 and UNS S32304 lean duplex stainless steels and UNS S32750 super duplex with AWS A5.3 BNi-7 (Ni–Cr–P) filler metal

Summary

Weld metals solidified in the ferritic-austenitic solidification mode (FA mode) have dual phases of ferrite and austenite in their as-solidified condition, where ferrite exhibits different morphologies depending on the chemical composition and welding conditions. This paper describes an investigation of the effect of the solidification and transformation sequence on the formation of final ferrite morphologies. Austenite is formed through either a eutectic reaction or peritectic reaction at the dendrite boundaries after the primary formation of ferrite. During the eutectic formation of austenite, the <100>_δ direction of the primary ferrite and the <100>_γ direction of the eutectic austenite are parallel to each other and lie along the growth direction of the primary dendrites. However, any specific lattice plane relationship between the two phases is not identified. During cooling after solidification, the austenite extends into the primary ferrite via solid-state transformation, and the final morphology of the ferrite is vermicular without any coherent orientation relationship between the primary ferrite and eutectic austenite. During peritectic formation of austenite, the Kurdjumov-Sachs orientation relationship is established between the primary ferrite and peritectic austenite, and the <100>_γ direction of the peritectic austenite is not parallel to the growth direction of the primary dendrites. During cooling after solidification, the primary ferrite transforms into austenite, and the final morphology of the ferrite is lathy, since the primary ferrite and peritectic austenite have a favourable coherent orientation.     

Effects of hot compression on carbide precipitation behavior of Ni—20Cr—18W—1Mo superalloy

The effect of hot compression on the grain boundary segregation and precipitation behavior of M₆C carbide in the Ni–20Cr–18W–1Mo superalloy was investigated by thermomechanical simulator, scanning electronic microscope (SEM) and X-ray diffraction (XRD). Results indicate that the amount of M₆C carbides obviously increases in the experimental alloy after hot compression. Composition analyses reveal that secondary M₆C carbides at grain boundaries are highly enriched in tungsten. Meanwhile, the secondary carbide size of compressive samples is 3–5 μm in 10% deformation degree, while the carbide size of undeformed specimens is less than 1 μm under aging treatment at 900 and 1000 °C. According to the thermodynamic calculation results, the Gibbs free energy of γ-matrix and carbides decreases with increase of the compression temperature, and the W-rich M₆C carbide is more stable than Cr-rich M₂₃C₆. Compared with the experimental results, it is found that compressive stress accelerates the W segregation rate in grain boundary region, and further rises the rapid growth of W-rich M₆C as compared with the undeformed one.     

Effects of Mm(NiCoAlMn)_5 hydrogen storage alloy coated with Ni-Co-P alloy by electroless plating on electrochemical properties of hydride electrodes

1　INTRODUCTIONNickel metalhydride (MH Ni)rechargeablebatterieswithhydrogenstoragealloysasthenegativeelectrodematerialhaveattractedincreasingattentionsbecauseofseveralinherentadvantages[16 ] .Sofar ,manymulti component,mischmetal based ,hydro gen storagealloyshavebeendevelopedtomeetthere quirementofhighcyclinglife ;theseincludesubstitu tionofthenickelbyMn ,CoandAl[7] .Thecomposi tionofthealloyisimportant ,andtheeffectsofsur facecompositionandmorphologyarealsosignificant.Micro encapsulat…     

Characteristics of stiffness and contact stress distribution of a spindle–holder taper joint under clamping and centrifugal forces

An understanding of the contact characteristics of a spindle–holder joint in machine tools calls for an in-depth analysis of its performance under machining conditions. This study specifically aims to model a spindle–holder taper joint to predict the stiffness and stress distribution under different clamping and centrifugal forces. A spindle–holder taper joint subjected to clamping and centrifugal forces was modeled using the finite element method. The stress distribution of the interface was revealed and it was found that the von-Mises stress had a non-linear distribution because of the clamping force of the holder. The centrifugal forces were included in the model to analyze the deformation of the joint. At high speed the centrifugal force caused a stress concentration at the large end of the holder. A typical 7/24 taper joint of a BT50 holder was investigated to identify the stiffness using a special experimental platform. The axial and radial stiffnesses, as well as the hysteresis cycles were obtained to predict the contact characteristics with different clamping forces. The experimental results showed that the model presented in this study was efficient in predicting the characteristics of the spindle–holder joint. The method presented is useful in identifying the dynamics of a spindle–holder and can thus be used to optimize the spindle system.     

Measurements of cold spray deposition efficiency

An analytical model of the kinetics of coating formation during cold spray is presented. The model is used to correct experimental data on deposition efficiency. The experimentally observed values are shown to be affected by experimental conditions, such as the velocity of substrate motion, the number of passes, the mass of a single portion of powder, and the exposure time of a given surface section. It is noted that experimental conditions can exert a significant effect on the consequences of the high-speed interaction of particles with a substrate. Relations are suggested that allow one to correct the results of deposition efficiency determined experimentally and to avoid mistakes in interpreting the data obtained.     

基于CEL方法的Al/Mg搅拌摩擦焊温度场及材料混合流动研究

本文基于耦合欧拉-拉格朗日(CEL)方法建立5A06铝合金与AZ31B镁合金对接搅拌摩擦焊（FSW）的全热力耦合数值模型,并结合试验测试对Al/Mg异种金属FSW过程的温度场及材料混合流动特征进行研究。数值模拟所得特征点的温度循环曲线、焊缝表面形貌以及横截面上异种材料的混合分布状态均与试验结果吻合良好。在此基础上,采用质点追踪法对材料混合流动行为进行了深入分析。结果显示,高温区集中分布在轴肩下方区域,返回侧(Mg侧)温度较低温度梯度较大。焊缝区上表面材料熔合线偏向于前进侧(Al侧)。搅拌针附近材料流动剧烈,前进侧和返回侧的大部分材料都较均匀地沉积于搅拌针后方。前进侧与返回侧材料在水平和竖直方向上的交叉混合流动,最终形成了两种材料“咬合式”的界面特征。     

Enthalpies of formation for the Al–Cu–Ni–Zr quaternary alloys calculated via a combined approach of geometric model and Miedema theory

A method to extrapolate the thermodynamic properties of quaternary alloys from constitutive binary systems is presented. The method is based on Miedema's theory, and the asymmetry of thermodynamic properties of constitutive binary alloys is considered in the present model. The dependence of asymmetric constituent on the choice in Toop model has been overcome. This method has been applied to calculate the enthalpies of formation for ternary alloys. In the present work, the proposed method is used to calculate the mixing enthalpies of Al–Cu–Ni–Zr quaternary alloys and its constitutive subsystems. The good agreement between calculation and experimental data indicates that the present method is reasonable for predicting the thermodynamic properties of multi-component system.     

Banded-like morphology and martensitic transformation of dual-phase Ni–Mn–In magnetic shape memory alloy with enhanced ductility

Two of the current challenges facing producers of Ni–Mn–In alloys are the achievement of small hysteresis and good ductility. Here, we present a dual-phase (β-Ni_51.8Mn_31.4In_16.8 and γ-Ni_62.4Mn_32.5In_5.1) Ni₅₂Mn₃₂In₁₆ alloy prepared by the zone melting liquid metal cooling directional solidification method, which simultaneously shows small hysteresis (ΔT < 10 K) and good ductility (6.6%). In addition, and more importantly, an inter-martensitic transition with a large magnetization jump occurs in this alloy. This is expected to further broaden the working temperature range of actuators and sensors that use this magnetic shape memory alloy. The sequence of the martensitic transformation can be shown by in situ X-ray diffraction to be austenite → 10M → 14M. Additionally, the second (γ) phase dramatically enhances the entropy change of these structural transformations and shifts them to higher temperatures. During the directional solidification, a novel banded-like microstructure, consisting of two layers, one of the β single phase and the other of the two phases coupled, forms at the low growth rate. A qualitative model is presented to explain the experimental observation, taking into account both the competitive nucleation and the growth of the phases. Experimental and theoretical analysis in the present work shows a linear relationship between the maximum spacing of the β single phase layer and the growth rate.     

快淬Nd—Fe—B粉末的TEM样品制备

将约３０％体积比的快淬Ｎｄ－Ｆｅ－Ｂ粉末分散混合在纯铝粉中,经过压坯、轧片、冲型、磨薄和离子溅射减薄,成功制备了快淬Ｎｄ－Ｆｅ－Ｂ粉末的ＴＥＭ样品。     

Effect of adding methods of metallic phase on microstructure and thermal shock resistance of Ni/（90NiFe2O4-10NiO） cermets

Ball mixing and electroless plating were respectively used as the adding methods of metallic phase to prepare Ni/（90NiFe2O4-10NiO） cermets for the inert anode in aluminum electrolysis. The microstructure and thermal shock resistance of cermet samples were studied. The results show that, for the samples prepared by ball mixing method, aggregation of metallic phase is found in either the green blocks or sintered samples and the extent of aggregation increases with the increase of metal content. For 6.5Ni/（90NiFe2O4-10NiO） cermets prepared with electroless plating method, the homogeneous and fine metallic particles are found in either the green compacts or sintered samples, but the relative density and thermal shock residual strength decrease by 3% and 28%-58% respectively, compared with samples prepared with ball mixing method.     

基于有限差分模型的磨削弧区流场动压力数值分析

磨削弧区动压力对通过磨削区磨削液的有效流量、润滑和冷却作用有重要影响。本研究基于流体动压理论,建立了磨削弧区的动压力分布数学模型,将微分方程简化至近似泊松方程形式后,采用有限差分法将连续方程离散化,得出了磨削区动压力的数值解,并提出了迭代优化算法,提高了计算效率。将砂轮特性参数纳入数学模型之中,可根据砂轮材质、砂轮与工件间隙、砂轮转速等参数预报磨削弧区的磨削液动压力分布。在此理论模型基础上,进行了验证实验,证明模型的科学性。结果表明:通过输入砂轮各项参数,该模型可以快速、准确地预报动压力的分布,为磨削加工提供参考。