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。     

pH值对脉冲电镀Ni-Cr-Mo合金镀层的影响

采用脉冲电镀法在Q235钢表面制备Ni-Cr-Mo合金镀层。利用辉光放电光谱仪(GDS)、扫描电镜(SEM)、Tafel曲线和电化学阻抗谱(EIS)考察了p H值对镀层元素含量、沉积速率、表面形貌和耐蚀性的影响。结果表明:随着p H值的增大,镀层中镍含量先减小后增大,铬先增大后减小,钼含量减小;镀层沉积速率先增大后减小;在3.5%Na Cl溶液中,镀层耐蚀性先增强后减弱。p H值为3.5时,镀层均匀致密,具有最大的自腐蚀电位(-0.535V)、最小的腐蚀电流密度(0.123μA·cm~(-2))和最大的电荷转移电阻(2550Ω·cm~2),此时镀层耐蚀性最好。     

占空比对脉冲电镀Ni-Cr-Mo合金镀层的影响

采用脉冲电镀法在Q235钢表面制备Ni-Cr-Mo合金镀层。利用辉光放电光谱仪(GDS)、扫描电镜(SEM)和Tafel曲线考察了占空比对镀层元素含量、沉积速率、表面形貌和耐蚀性的影响。结果表明:随占空比的增大,镀层镍、钼含量增大,铬含量减小,沉积速率减小;在3.5%Na Cl溶液和6.0%Fe Cl3溶液中,耐蚀性减弱。相比于6.0%Fe Cl3溶液,镀层在3.5%Na Cl溶液中耐蚀性更好。     

添加剂对脉冲电镀Ni-Cr-Mn合金镀层的影响

采用脉冲电镀法在Q235钢表面制备Ni-Cr-Mn合金镀层。利用辉光放电光谱仪(GDS)、扫描电镜(SEM)、Tafel曲线和电化学阻抗谱(EIS),考察了添加剂对镀层元素含量、沉积速率、镀层外观、表面形貌和耐蚀性的影响。结果表明:随添加剂含量的增大,镀层中镍含量降低,铬、锰含量增加;沉积速率先增大后减小;镀层外观光亮度先升高后降低;晶粒尺寸先减小后增大;在3.5%Na Cl溶液中,镀层耐蚀性先增强后减弱。添加剂含量为10 ml/L时,镀层致密均匀,具有最大的腐蚀电位(-0.363 V)、最小的腐蚀电流密度(8.829×10-8A·cm~(-2))和最大的电荷转移电阻(2737Ω·cm~2),耐蚀性最好。     

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。     

脉冲频率对Zn-Ni-Mn合金镀层的影响

采用脉冲电镀法在Q235钢表面制备Zn-Ni-Mn合金镀层,研究脉冲频率对Zn-Ni-Mn合金镀层元素组成、沉积速率、表面形貌及耐腐蚀性的影响。结果表明,随脉冲频率的增大,Zn-Ni-Mn合金镀层中锰含量增大,锌、镍含量减小;沉积速率先升高后降低;晶粒尺寸减小;耐腐蚀性先增强后减弱。脉冲频率为1000 Hz时制备的Zn-Ni-Mn合金镀层耐蚀性最好。     

脉冲电镀Ni-Cr-Mo合金镀层施镀时间的研究

采用脉冲电镀法在Q235钢表面制备Ni-Cr-Mo合金镀层。利用扫描电镜(SEM)、辉光放电光谱仪(GDS)、Tafel曲线和电化学阻抗谱(EIS)考察了施镀时间对镀层表面形貌、形成过程、镀层厚度、元素含量和耐蚀性的影响。结果表明:镀层由粒状结构形核、长大并逐层叠加形成;镀层的形成存在一个孕育期,孕育期后一定时间内镀层增厚较为困难,施镀时间继续增大,镀层可顺利增厚。随施镀时间的增大,镀层镍含量增大,铬含量减小,钼含量减小。在3.5%NaCl溶液中,镀层耐蚀性先增强后减弱。施镀时间为50 min时制备的镀层具有最大的自腐蚀电位(-0.355 V)、最小的腐蚀电流密度(0.006μA·cm~(-2))和最大的电荷转移电阻(26544Ω·cm~2),耐蚀性最好。     

脉冲电镀Ni-Cr-Mn合金镀层配位剂的研究

利用脉冲电镀方法在Q235钢表面制备Ni-Cr-Mn合金镀层。采用辉光放电光谱仪、电化学工作站等设备,研究了不同的配位剂:甲酸铵、柠檬酸铵、复合配位剂A对Ni-Cr-Mn合金镀层成分、沉积速率及耐蚀性的影响。结果表明,三种不同的配位剂对Ni-Cr-Mn合金镀层成分、沉积速率及耐蚀性的影响相同。随着配位剂含量的增加,镀层中Cr、Mn含量先升高后降低,Ni含量先降低后升高;然而沉积速率先升后降;复合配位剂A制备的Ni-Cr-Mn合金镀层,具有最小的腐蚀电流密度、最大的腐蚀电位,分别为9.374×10~(-8)A/cm~2、-0.288 V,耐蚀性更佳。     

电流密度对脉冲电镀Zn-Ni-Mn合金镀层的影响

通过脉冲电镀技术在Q235钢基体上制备出Zn-Ni-Mn合金镀层。研究了电流密度对镀层表面形貌、成分、沉积速率及耐蚀性的影响。结果表明,随着电流密度的增大,沉积速率先增大再减小;镀层中锰含量升高,锌、镍含量降低。随电流密度增加,该镀层随耐蚀性先增强后减弱。电流密度为3.0 A·dm~(-2)时,所得Zn-Ni-Mn合金镀层平整致密,耐蚀性最好。Zn-Ni-Mn合金镀层在3.5%NaCl溶液中的耐蚀性比在5.0%NaOH溶液中更好。     

施镀时间对脉冲电镀Zn-Ni-Mn合金镀层的影响

采用脉冲电镀法在Q235钢表面制备Zn-Ni-Mn合金镀层。利用辉光放电光谱仪(GDS)、扫描电镜(SEM)、塔菲尔(Tafel)曲线和电化学阻抗谱(EIS)研究了施镀时间对合金镀层元素含量、沉积速率、表面形貌及耐蚀性的影响。结果表明:随施镀时间的延长,镀层中锌、镍含量降低,锰含量升高;镀层沉积速率增大;镀层耐蚀性先增强后减弱。施镀时间20 min所得镀层均匀致密,耐蚀性最佳。在最佳施镀时间20 min下所制备的Zn-Ni-Mn合金镀层与Zn-Ni合金镀层相比,其自腐蚀电位更正,自腐蚀电流密度更低,具有更加优异的耐蚀性。     

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。