脉冲电镀Ni-Sn-Mn合金镀层工艺参数优化及耐蚀性

采用脉冲电镀技术在Q235钢表面沉积制备Ni-Sn-Mn合金镀层,通过正交试验方法对工艺参数进行了优化。利用辉光放电光谱仪(GDS)、扫描电镜(SEM)、X射线衍射仪(XRD)、Tafel曲线和EIS谱考察镀层元素含量、镀速、表面形貌、相结构及耐蚀性。结果表明:脉冲电镀Ni-Sn-Mn镀层最佳工艺参数为:镀液温度30℃,电流密度10 A·dm~(-2),施镀时间30 min,p H值4.0。最佳工艺条件下所得镀层为非晶态结构,表面球胞颗粒均匀致密,Ni、Sn、Mn的质量分数为68.59%、22.17%、9.24%。与Ni-Sn镀层相比,Ni-Sn-Mn镀层在3.5%Na Cl腐蚀液中的E_(corr)值(-0.346 V,vs Al/Ag Cl电极)更正,I_(corr)值(2.518×10~(-8)A·cm~(-2))更低,R_(ct)值(11 265Ω·cm~2)更大,耐蚀性更好。     

纳米TiC浓度对双脉冲电沉积Ni-TiC复合镀层结构及性能的影响

研究了镀液中纳米TiC的添加量对双脉冲电沉积Ni-TiC复合镀层结构及性能的影响。通过扫描电镜(SEM)和X射线衍射(XRD)对镀层的表面形貌和物相进行了表征,并研究了镀层的表面粗糙度、显微硬度、耐磨性能和耐腐蚀性能。结果表明：当镀液中TiC浓度较低时,复合镀层表现为类似于纯Ni镀层的胞状沉积结构。当镀液中TiC浓度较高时,复合镀层表现为菜花状沉积结构。当纳米TiC浓度为8 g/L时,镀层表面致密性相对较高,Ni的衍射峰有明显的宽化现象。随着镀液中纳米TiC浓度的升高,复合镀层的磨损质量损失比表现为先下降后上升的趋势,当TiC浓度为8 g/L时,磨损质量损失比最小,为5.436%。当镀液中纳米TiC浓度为8 g/L时,镀层的自腐蚀电流密度最小,极化电阻值最大。结果表明双向脉冲电沉积制备Ni-TiC复合镀层镀液中最佳纳米TiC浓度为8 g/L。     

化学镀Ni-Mo-P合金镀工艺及镀层性能

为了改善化学镀Ni-Mo-P工艺中沉积速度慢、镀层硬度低、耐腐蚀性差等问题,试验研究了镀液组分、pH值、络合剂、表面活性剂、稳定剂对化学镀Ni-Mo-P合金镀层硬度、沉积速度、耐蚀性、孔隙率的影响,得出最佳的镀液配方和工艺参数:2.4 g/L Na2MoO4,26.2 g/L NiSO4·6H2O,10.6 g/L NaH2PO2·H2O,1 mg/L KI,30 g/L柠檬酸三钠,9 g/L乳酸,50 mg/L十二烷基苯磺酸钠,pH8.5,温度90℃.本结果为化学镀Ni-Mo-P合金工艺提供了依据,较有实用价值.     

柠檬酸铵浓度对脉冲电镀Ni-Cr-Mo合金镀层的影响

目的揭示柠檬酸铵浓度对脉冲电镀Ni-Cr-Mo合金镀层元素含量、沉积速率、表面形貌和耐蚀性的影响规律。方法采用脉冲电镀法在Q235钢表面制备Ni-Cr-Mo合金镀层,利用辉光放电光谱仪、扫描电镜、Tafel曲线和电化学阻抗谱考察柠檬酸铵浓度对镀层元素含量、沉积速率、表面形貌和耐蚀性的影响。结果随柠檬酸铵浓度的增大,镀层镍含量减小,铬、钼含量增大,镀层沉积速率减小,镀层表面颗粒的尺寸减小,镀层在3.5%Na Cl溶液中的耐蚀性先增强后减弱。结论柠檬酸铵质量浓度为196 g/L时,镀层具有最大的自腐蚀电位(-0.537 V)、最小的腐蚀电流密度(0.313μA/cm~2)和最大的电荷转移电阻(2075?·cm~2),耐蚀性最好。     

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 通过扫描电镜、电化学分析和腐蚀失重等方法，研究了镀液中添加RE对双脉冲电沉积法获得镍镀层的耐蚀性影响。结果表明：镀液中添加适量的RE，可使镀层组织细小且表面平整致密，耐蚀性提高，当镀液中含RE量为0.25 g/L时，镀层耐蚀性较好。     

脉冲电沉积时间对Sn-Zn-Mn合金镀层的影响

为了提高低碳钢在海洋环境下的耐蚀性,采用脉冲电沉积技术在Q235钢表面成功沉积出Sn-Zn-Mn镀层。利用辉光放电光谱仪(GDS)、扫描电镜(SEM)、塔菲尔(Tafel)极化曲线和电化学阻抗谱(EIS)考察了施镀时间对元素成分、镀速、表面形貌、阴极电流效率和耐蚀性的影响。结果表明:随施镀时间的增加,w(Sn)和w(Zn)减小,w(Mn)增大;镀速和沉积电流效率呈先增大后减小的趋势;镀层胞状颗粒尺寸增大;耐蚀性先提高后降低。施镀时间为30 min时,所得Sn-Zn-Mn镀层表面平整光滑、组织均匀致密,在3.5%Na Cl腐蚀液中具有最正的E_(corr)值(-0.394 V)、最低的I_(corr)值(1.585×10~(-8)A·cm~(-2))和最大的R_(ct)值(8653Ω·cm~2),耐蚀性最好。     

AZ91镁合金表面制备Ni-SiO2纳米复合电镀层的工艺研究

采用复合电沉积技术在AZ91镁合金表面制备Ni-SiO2纳米复合镀层,并研究各工艺参数对镀层的影响,从而得出最佳工艺.研究结果表明:在镀液中纳米SiO2的添加量为20 g/L,阴极电流密度为1.0 A/dm2,镀液温度为50℃,活性剂A的添加量为1.0 g/L,pH为5～6的条件下,经过20～30 min电沉积,可获得均匀、平滑的镀层,镀层的显微硬度与耐蚀性最佳.     

快速化学镀 Ni-Zn-P 合金工艺及镀层性能

目的确定快速化学镀Ni-Zn-P合金的工艺。方法通过一系列实验,研究主盐含量、pH值、温度、时间等对镀层沉积速度及镀层锌镍比的影响,确定最优工艺条件。借助SEM,EDS,XRD及电化学方法分析镀层微观形貌、成分及耐蚀性。结果在ZnSO4·7H2O8 g/L,NiSO4·6H2O 35 g/L,NaH2PO2·H2O20 g/L,NH4Cl 50 g/L,C6H5Na3O7·2H2O 70 g/L,稳定剂1.5 mg/L,p H=9.0,温度90~95℃的条件下,化学镀Ni-Zn-P合金沉积速度为5~6μm/h,镀层中Zn质量分数为8%~10%,P质量分数为6%左右,Ni质量分数为80%~85%。Zn的存在使Ni呈现出晶态结构,在XRD谱图上2θ=45°及2θ=52°位置分别出现了Ni(111),Ni(200)衍射峰。施镀时间不会影响镀层成分,但会影响镀层耐蚀性。施镀1.5 h时,镀层厚度约为9~10μm,其耐蚀性略好于相同厚度的Ni-P镀层。结论 Ni-Zn-P化学镀沉积速度较快,8%~10%的Zn使镀层中Ni呈晶态结构,且改善了镀层耐蚀性。     

电沉积方式对Ni-Cr-Mn合金镀层耐蚀性的影响

采用直流、单脉冲和换向脉冲三种不同电沉积方式在Q235钢表面电镀制备Ni-Cr-Mn合金镀层。利用辉光放电光谱仪、形状测量激光显微系统、Tafel曲线和电化学阻抗谱,研究了电沉积方式对镀层元素含量、沉积速率、3D形貌和耐蚀性的影响。结果表明:按照直流、单脉冲和换向脉冲的顺序,镀层中镍含量减小,铬、锰含量增大,沉积速率先增大后减小,表面粗糙度降低,耐蚀性增强。直流方式制备的镀层表面存在个别较大的颗粒,单脉冲方式制备的镀层表面颗粒大小较为均匀,但仍存在个别较大颗粒,换向脉冲方式制备的镀层总体均匀致密。换向脉冲方式制备的镀层表面粗糙度最低,在3.5%NaCl溶液中,该镀层具有最大的腐蚀电位(-0.305 V)、最小的腐蚀电流密度(7.467×10~(-8)A·cm~(-2))和最大的电荷转移电阻(5972Ω·cm~2),耐蚀性最佳。     

尿素含量对脉冲电镀Ni-Cr-Mo合金镀层的影响

采用脉冲电镀法在Q235钢表面制备了Ni-Cr-Mo合金镀层。利用辉光放电光谱仪、扫描电镜、Tafel曲线和电化学阻抗谱考察了尿素含量对镀层元素含量、沉积速率、表面形貌和耐蚀性的影响。结果表明,随尿素含量的增大,镀层镍含量先增大后缓慢减小,铬含量先增大后减小、钼含量先减小后增大;镀层沉积速率先增大后减小;镀层表面颗粒尺寸减小;镀层在3.5%NaCl溶液中耐蚀性先增强后减弱。尿素含量为60 g·L~(-1)时制备的镀层具有最大的自腐蚀电位(-0.535 V)、最小的腐蚀电流密度(0.123μA·cm~(-2))和最大的电荷转移电阻(2 550Ω·cm~2),耐蚀性最好。     

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。