环氧铝粉涂层在3.5%NaCl介质中的失效机理研究

采用电化学阻抗谱技术（EIS）研究了环氧铝粉涂层/Q235钢基体在3.5 %NaCl介质中的电化学腐蚀行为.利用扫描电镜（SEM）分析了涂层表面形貌,对涂层断面进行了能谱（EDX）线扫描和界面处腐蚀产物成分分析,探讨了环氧铝粉涂层的腐蚀失效机理.结果表明,腐蚀介质能通过涂层迅速渗透到涂层/基体界面,引起涂层电阻值的降低及界面处电化学腐蚀的开始.失效前涂层致密、连续,失效后涂层表面出现鼓泡、孔洞等现象.鼓泡是由腐蚀产物的体积膨胀和腐蚀介质渗入产生的压力推动共同产生的.界面处腐蚀产物主要是Fe和Al的氧化物及氯化物.涂层的失效机理为腐蚀介质渗入,涂层鼓泡、剥离.     

化合物CeCl_2对4Cr5MoV1Si钢气体软氮化过程的影响及生产应用

在通氨滴醇气体软氮化的基础上加入不同量的稀土化合物CeCl_2,研究了它对动力学过程、渗层组织结构,硬度及耐磨性的影响.结果表明:与常规软氮化过程相比,CeCl_2可使渗速提高20～30％,渗层的N、C含量增高,且向内层延伸分布,使表面硬度和耐磨性大大挺高;稀土元素Ce亦被渗入钢的表面,不仅起到催化活化渗入介质的作用,同时还可能起到微合金化的作用。     

X70管线钢近中性环境氢致开裂与阳极溶解的关系

采用慢速率拉伸试验(SSRT)方法及电化学测量技术,研究了阴极电位下X70钢在某种近中性介质中的应力腐蚀开裂(SCC)机理.试验表明,在近中性介质中,随着电位的降低,管线钢的SCC敏感性增强.但当电位低于某一范围后,SCC敏感性减弱;随着溶液pH值的降低,管线钢的腐蚀速率增大,敏感电位区间负移.分析表明,在近中性介质中,管线钢应力腐蚀开裂主要受阳极溶解和氢致开裂两种机理的联合作用,氢的渗入可能与氢的还原过程及管线钢阳极溶解密切相关.适宜的电位可以使阳极溶解和氢的联合作用增强.增强应力腐蚀开裂倾向.     

冷轧带钢电镀后表面起泡原因的分析

冷轧带钢在氰化物碱性介质中电镀锌后,基材表面出现间断的呈直线排列小鼓泡,经扫描电子显微镜观察和能量色散谱检测,发现气泡内有一大小约10μm以Mg的氧化物为主的块状物.在电镀过程中,由于氢原子的渗入引起基材表层起泡.     

在氮化过程中扩散层性能的形成特性

在氮化方面,大部份文章是研究氮化完成后的组织和性能,而且一般仅在室温状态下研究。在这种情况下,钢的成份,渗入介质的成份,渗入的条件均已改变。因而氮化过程的动力学机构,以及被处理零件(试样)的性能,是按最后的效果来确定。     

温度梯度下介质在高分子平板材料中的扩散

<正> 一、引言 目前高分子材料耐腐蚀性能的测定主要采用静态浸泡法,虽然其数学处理简便,但往往不能反映真实情况,动态耐腐蚀研究是今后发展的方向,它能较真实地反映高分子材料内存在温度梯度时的介质扩散情况。奥田聡曾对在温度梯度下渗入介质的浓度分布与着色深度关系作过报导。     

SOM人工神经网络与阻抗谱方法结合研究涂层的失效过程

    分析了干湿循环条件下有机涂层的电化学阻抗谱特征后选取了阻抗变化率参数作为一维自组织特征映射(self-organizing feature map,SOM)神经网络的训练样本,每个样本对输出层神经元都会产生一定的激发水平,根据该神经网络的特性,输出神经元激发水平的变化趋势便可以反映涂层的降解过程.结合涂层阻抗谱的变化特征,可以把干湿循环条件下涂层的失效过程分为三个阶段,即介质渗入涂层过程,介质到达金属表面诱发金属腐蚀过程和腐蚀扩展涂层剥离过程.     

结构钢的氢脆

在毛坯生产工艺过程中(熔炼、焊接、电镀、酸洗等)氢会渗入钢内。在高温、高压与辐射等其他因素的共同作用下,在含氢介质中工作的设备体积也要增大。这些情况为氢渗入钢内创造了条件。氢脆的产生是由于溶入金属中的游离氢向位错移动,并使这些位错“钉扎”的结果。所以氢带来的主要不良影响是在变形速度不大的条件下,材料塑性降低。这时氢的扩散速度与位错运动速度大致相等。     

钨铜/铍青铜异质钎焊界面组织与性能

采用BAg56CuZnSn,BAg50ZnCdCuNi和BAg49ZnCuMnNi银钎料实施了钨铜合金/铍青铜异质材料接头的感应钎焊连接,研究了其钎焊界面组织与力学性能.结果表明,3种银钎料均能获得完好界面钎焊接头,钎料与钨铜和铍青铜形成较好冶金结合.钎料与铍青铜界面冶金结合充分,形成明显互扩散区.钎料与钨铜钎焊界面清晰,且钎料向钨铜近界面区域形成明显扩散渗入现象.强度测试表明,BAg49ZnCuMnNi钎焊接头强度最高,达到250 MPa,接头断裂均发生在钨铜侧钎焊界面.分析表明,钎料向钨铜渗入明显促进界面结合,钎料中添加镍,由于镍与钨的扩散互溶进一步提高界面冶金结合,Mn元素添加明显细化钎缝晶粒,接头强度显著提升.     

Ti-37.5Zr-15Cu-10Ni钎焊钼的钎缝组织分析

采用Ti-37.5Zr-15Cu-10Ni非晶钎料真空钎焊钼,获得Mo/Mo钎焊接头,研究钎焊过程液态钎料与母材的相互作用. 结果表明,液态Ti-37.5Zr-15Cu-10Ni钎料与钼发生扩散–溶解,即母材钼向钎料中的溶解和钎料组分向母材的扩散. 随钎焊温度的升高,钼向钎料中溶解量增加,凝固后钼主要固溶在Ti基固溶体内;随钎焊温度的升高,发生钎料组分向母材晶间的扩散,当温度为900 ℃时,发生显著的晶间渗入现象. 为得到良好的钎焊接头,避免母材过量溶解和晶间渗入的发生,Ti-37.5Zr-15Cu-10Ni钎料真空钎焊钼温度不宜高于900 ℃.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。