A1-Zn-In-Mg-Ga-Mn牺牲阳极腐蚀防护行为研究

采用电化学阻抗谱技术、失重法和扫描电镜分析技术(SEM)研究Al-Zn-In-Mg-Ga-Mn牺牲阳极在自腐蚀与7A52铝合金偶接两种条件下的溶解行为和活化性能。结果表明:偶连接的Al-Zn-In-Mg-Ga-Mn牺牲阳极有效地降低了7A52Al的腐蚀速率,牺牲阳极一直存在活性溶解,腐蚀均匀,腐蚀产物易脱落。自腐蚀的Al-Zn-In-Mg-Ga-Mn牺牲阳极发生局部腐蚀,表面溶解不均匀;表面腐蚀产物和氧化膜以及活性溶解点的减少阻滞了牺牲阳极溶解反应。     

微量锑和锡对铝基牺牲阳极材料性能的影响

熔炼了添加合金元素Sb和Sn的5种Al-Zn-In系牺牲阳极材料,采用恒电流方法测试了其电化学性能,采用金相显微镜、扫描电镜和能谱分析分别观察和分析了阳极材料的显微组织和组成.结果表明:Sb具有细化晶粒的作用,但晶界存在较多偏析相,电流效率偏低;与Sb相比较,Sn也具有细化晶粒的作用,电流效率有所提高,晶界偏析相较少,但阳极的表面腐蚀溶解不均匀;Sn和Sb的协同作用在于能有效地抑制Si的偏析,显著提高阳极的电流效率,使得阳极表面具有良好的腐蚀溶解性.     

固溶处理对Mg-6Al-5Pb-1.5In阳极腐蚀电化学性能的影响

在3.5%NaCl(质量分数)溶液中测定铸态和经固溶处理的Mg-6Al-5Pb-1.5In镁合金阳极的腐蚀电化学性能,采用金相(OM)、扫描电镜(SEM)和能谱分析(EDS)分别研究其显微组织、截面腐蚀形貌及相组成。结果表明:固溶后β-Mg17Al12相基本溶入α-Mg基体,降低微电偶腐蚀中阴极与阳极的面积比,增大阳极自腐蚀速率;Mg2Pb相的自腐蚀电位比镁基体正,固溶后Pb以Mg2Pb相析出,阳极表面腐蚀后晶粒中央的Mg2Pb相并没有被腐蚀。Al含量是决定镁阳极中各相腐蚀速率的关键,相表面形成的保护膜中Al含量越高,对基体保护性能越好。     

纯铁对B10和B30铜合金在模拟海洋环境中的阴极保护

测试了模拟海洋环境中B10、B30铜合金及纯铁的电化学性能,采用恒电流法测试了纯铁牺牲阳极性能,并结合电偶腐蚀试验进一步分析了采用纯铁对B10、B30铜合金进行阴极保护的可行性。结果表明:纯铁的自腐蚀电位低于B10和B30铜合金的,牺牲阳极性能良好,有稳定工作电位,电流效率高;电偶腐蚀试验中,纯铁作为阳极材料极大地抑制了B10、B30铜合金的腐蚀,起到了良好的阴极保护效果。     

Al-Zn-In-Si牺牲阳极在模拟海水及海泥环境中的电化学性能

目的 分析A13型Al-Zn-In-Si牺牲阳极在海水、海泥中的电化学性能.方法 采用恒电流极化进行4 d的加速实验,使用电化学阻抗谱(EIS)分析电化学腐蚀过程,通过扫描电子显微镜(SEM)、能谱分析(EDS)及三维超景深显微镜观察分析腐蚀形貌及表面化学成分,对比研究了Al-Zn-In-Si牺牲阳极在模拟海水和海泥环境下的腐蚀形貌、电化学性能.结果 在模拟海水和海泥环境中,尽管Al-Zn-In-Si牺牲阳极都满足DNVGL-RP-B401的要求,但在海泥环境中,其电化学效率仅为65.97％,远低于海水环境中的89.43％.牺牲阳极在海水环境中发生均匀腐蚀,而在海泥环境中却呈现严重的不均匀腐蚀现象,表面腐蚀坑为疏松多孔蜂窝状.结论 在海泥环境下,Al-Zn-In-Si牺牲阳极的腐蚀产物扩散困难,局部呈现腐蚀坑,自腐蚀速率高,导致电化学效率降低.溶解过程中,由于组织脱落,自身消耗增加,电化学容量降低,从而导致阳极在模拟海泥环境中的电化学性能低于海水环境,并揭示了阳极在模拟海水、海泥环境中的腐蚀机理.     

温度和pH对Al-Zn牺牲阳极在某生产水中电化学腐蚀性能的影响

测试了Al-Zn牺牲阳极在某生产水不同条件下的开路电位、极化曲线和循环伏安曲线,并结合牺牲阳极表面腐蚀形貌进行了分析。结果表明,随生产水温度升高,牺牲阳极开路电位负移,自腐蚀倾向增大,在所测温度范围内牺牲阳极腐蚀回路的腐蚀速率均受阳极控制,且在48℃时腐蚀电流密度(Jcorr)要比常温下大一个数量级,而当温度为42℃和48℃时,均易产生晶间腐蚀;随生产水pH升高,牺牲阳极开路电位先正移后负移,该腐蚀回路的腐蚀速率由原来的阳极控制变成阴极控制或混合控制,且其大小先减后增。     

铝合金牺牲阳极在淡海水环境下腐蚀产物及其形成过程分析

铝合金牺牲阳极以其广泛的材料来源和低廉的价格,在江河入海口等淡海水区域的近海钢管桩、海底隧道钢壳中的应用日趋广泛。淡海水环境下铝合金牺牲阳极腐蚀产物会在铝合金牺牲阳极表面的附着对牺牲阳极的应用产生干扰,本文通过对铝合金牺牲阳极在淡海水环境下的加速腐蚀实验,定性分析了铝合金牺牲阳极在淡海水环境下腐蚀产物的成分和形成过程。     

Mg-Mn高电位牺牲阳极的腐蚀行为

采用金属型铸造了3种成分的梯形高电位Mg-Mn牺牲阳极.通过模拟土壤环境中[饱和CaSO4-Mg(OH)2溶液]的恒电流腐蚀试验,研究了Mg-Mn牺牲阳极的腐蚀行为.结果表明,Mg-Mn牺牲阳极中杂质元素存在较大的溶质偏析和明显的晶粒尺寸差异,导致距离模具表面不同距离处的电流效率不同.杂质元素在晶界上不均匀分布,使Mg-Mn阳极产生晶间腐蚀,第二相粒子不均匀程度越大,未腐蚀部分机械剥落越严重,从而加大阳极的质量损失,降低了阳极的电流效率.腐蚀形貌观察发现,当Mg阳极表面呈现出条状的蚀坑时,机械剥落现象严重,腐蚀很不均匀,电流效率较低,仅为41％;Mg阳极的表面蚀孔孔径越细小,分布越均匀,电流效率越高.     

深海低温高压条件下铝合金牺牲阳极电化学性能研究

牺牲阳极的阴极保护法是海洋环境下控制钢结构腐蚀有效的方法,电流效率与电位稳定性是鉴别牺牲阳极电化学性能优劣的重要指标。本文使用了电流效率测试和表面形貌观察等方法,测试分析了三种不同成分铝合金牺牲阳极在低温高压海水环境中的电化学性能,结果表明:三种成分的铝合金牺牲阳极都具有较高的电流效率,其中成分3的铝合金牺牲阳极表面溶解最均匀,呈现均匀溶解形貌,未见明显蚀坑和晶间腐蚀现象。     

固溶处理对Al-Zn-Bi-Sn合金组织和电化学性能的影响

将Al-5Zn-0．5Bi-0．03Sn合金在550℃保温10h水淬固溶处理,采用扫描电镜（SEM）和能谱分析（EDX）研究了固溶前后组织形貌和析出相成分,利用CHI660C电化学工作站测试固溶处理前后该牺牲阳极材料的电流效率、在3．5％NaCl溶液中的极化曲线及电化学阻抗谱（EIS）。结果表明,固溶处理后Al-5Zn-0．5Bi-0．03Sn合金牺牲阳极材料电流效率提高了19．57％,铝合金阳极沿晶界分布的偏析相发生球化且偏析相中Zn、Sn元素溶入基体;固溶后合金自腐蚀电位和自腐蚀电流密度均降低;等效电路RS（CRP（QRD））较好地拟合了Al-5Zn-0．5Bi-0．03Sn合金在3．5％NaCl溶液中腐蚀的EIS谱．基本反映了该牺牲阳极材料的电极反应过程。     

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。