稀土镧不同化合物对渗锌层耐蚀性能的影响

目的 研究稀土元素镧的不同化合物对渗锌层耐蚀性的影响.方法 在渗锌剂中不添加稀土元素及分别添加氧化镧、硫酸镧、氯化镧和硝酸镧,采用包埋法制备相关的渗锌层.通过使用TT260覆层测厚仪测量渗层厚度,利用SEM对渗锌层的表面形貌进行观察.配制质量分数为5%的NaCl溶液,进行全浸腐蚀试验,使用TG-328 A分析天平测量浸泡75 h和150 h的腐蚀失重,计算腐蚀失重速率,使用数码显微镜观察渗锌层腐蚀形貌.结果 与未添加稀土元素制备渗锌层的厚度33.0μm相比,在渗锌剂中添加稀土元素镧能够有效提高渗层厚度,添加氧化镧的渗层厚度上升至45.7μm,添加硫酸镧的渗层厚度上升至41.7μm,添加氯化镧的渗层厚度上升至36.1μm,添加硝酸镧的渗层厚度上升至43.1μm.观察不同渗锌剂制备渗锌层的表面形貌,添加氧化镧制备的渗锌层表面最均匀、致密,但渗层表面出现少许微裂纹.在盐水浸泡实验中,添加硝酸镧制备渗锌层的腐蚀失重速率在浸泡75 h和150 h时都是最小的,分别为0.0441 g/(m2·h)和0.0625 g/(m2·h),表现出十分优异的耐蚀性能.结论 在渗锌剂中添加稀土元素镧,能够提高渗锌的效率,改善渗锌层的表面质量,使得渗层更加均匀、致密,但渗层表面会出现少许不同程度的微裂纹.氧化镧、硫酸镧和硝酸镧的催渗作用十分明显,氯化镧的催渗效果最差.在耐盐水环境的腐蚀中,添加氯化镧制备的渗锌层的耐蚀性最不理想,而添加硝酸镧制备的渗锌层的耐蚀性最好.     

Na_2SO_4沉积引起的Fe─10Cr合金在700℃的热腐蚀

研究了涂有Ｎａ２ＳＯ４盐膜的Ｆｅ－１０Ｃｒ合金在７００℃，Ｏ２－０．５％（ＳＯ２＋ＳＯ３）气氛中的热腐蚀行为。结果表明，该合金在实验条件下发生了“低温”热腐蚀。腐蚀产物分两层，即在熔盐中沉积出的疏松氧化物层和在合金表面直接成长的相对致密的氧化物层。腐蚀形貌观察说明，热腐蚀的发展主要伴随着致密氧化层的增厚。腐蚀动力学和腐蚀形貌特点支持热腐蚀的电化学机理模型。     

模拟北极航线多因素耦合条件下船用低合金钢的腐蚀行为

目的 研究船舶低合金钢在模拟南海到北极的航行过程中的腐蚀情况,探索它在环境交变条件下的腐蚀行为与机理。方法 选用3种温度（37、25、4℃）及相对应的典型海洋细菌,包括大西洋假交替单胞菌（Pseudoalteromonasatlantica）、需钠弧菌（Vibrionatriegens）和养料嗜冷杆菌（Psychrobactercibarius）,模拟航行往返过程中海洋环境的变化情况,以21d为一个实验周期,每7d改变一次温度和细菌种类,采用扫描电镜（SEM）、白光干涉、失重法和电化学测试方法从宏观和微观两方面对材料的腐蚀行为进行表征分析。同时,将相同的低合金钢试样浸泡在无菌海水中进行对照实验。结果 浸泡在无菌海水中,当初始温度为37℃时,低合金钢的初始腐蚀速率较大;随着温度的降低和时间的延长腐蚀速率逐渐减小;当初始温度为4℃时,低合金钢的点蚀情况较严重,但腐蚀速率变化不大。浸泡在有菌海水中,初始温度为37℃时,低合金试样表面有大量方解石结构的碳酸钙镁盐沉积,从而较好地抑制了均匀腐蚀和点蚀的发生;当初始温度为4℃时,低合金钢试样表面点蚀严重,EDS能谱分析证明低合金钢试样在低温环境中没...     

电化学方法研究锈层覆盖下碳钢的腐蚀规律

分别采用失重法与电化学方法(包括极化曲线、线性极化法和电化学阻抗技术)研究了碳钢在海水中浸泡48周的腐蚀规律。结果发现,短期浸泡在海水中的碳钢,表面生成的腐蚀产物薄且疏松,长期浸泡后,锈层逐渐分为两层:外锈层薄且疏松,内锈层厚且致密。短期浸泡,失重法与电化学方法得到的腐蚀规律一致,腐蚀速度逐渐减小并且数值相近,此时电化学方法可以用来准确的估算碳钢的腐蚀速度。长期浸泡,电化学方法测定的腐蚀速度转为逐渐增大,偏离了失重结果,并且锈层越厚偏差越大,此时电化学方法会过高估算腐蚀速度。     

带锈碳钢在流动海水中的长期腐蚀行为

将Q235碳钢在流动海水中浸泡280 d,利用失重法和多种腐蚀电化学方法研究了其在浸泡过程中的腐蚀规律.结果表明,与静止海水浸泡相比,在流动体系长时间浸泡后,电极表面几乎不存在疏松的黄色锈层,而被一层致密的黑色腐蚀产物所覆盖;失重法测得的腐蚀速率随腐蚀时间延长呈现减小的趋势,并最终趋于稳定,与静止海水相比,流动海水中的腐蚀速率高出约1倍;电化学方法测得的腐蚀速率则随浸泡时间的延长而增大,与失重法的结果之间存在较为明显的偏差,并且浸泡时间越长,这一偏差越明显.长期浸泡后,碳钢表面的锈层对电化学测试结果产生影响,是导致电化学方法不能准确评估腐蚀速率的原因.     

H2S水溶液中的腐蚀与缓蚀作用机理的研究：Ⅰ.酸性H2S溶液 …

利用交流阻抗（ＥＬＳ）和极有化曲线结合扫描电镜（ＳＥＭ）和能谱分析,对常温下低碳钢在含Ｈ２Ｓ的模拟炼厂常减压塔横张水中的腐蚀电化学行为和不同浸泡时间下硫化物膜的生长过程进行了研究。结果表明,Ｈ２Ｓ对腐蚀反应的阴极过程有很大的促进作用,搅拌条件下尤甚;随介质ＰＨ值升高,其腐蚀性减弱。腐蚀浸泡初期（小于８ｈ）,电极表面硫化物膜的生长尊循抛物线机制,随浸泡时间的延长,硫化物膜变得疏松、易于破裂和脱落,并     

镁合金低能耗微弧氧化膜层组织结构及耐蚀性的试验研究

在镁合金表面试制了低能耗微弧氧化膜层,通过SEM、TEM及电化学腐蚀、盐水浸泡失重测试,对低能耗微弧氧化膜层的组织结构及耐蚀性能进行了研究。结果显示,低能耗电解液中制备的微弧氧化膜层与普通微弧氧化膜层表面形貌存在明显差异;前者的主要成分是非晶相而不是Mg O晶体相;电化学腐蚀及盐水浸泡失重试验结果同时显示,低能耗微弧氧化膜层的电化学腐蚀性能与常规微弧氧化膜层的差别不大,两种膜层都可以对镁合金基体起到良好的保护作用。     

Q235碳钢表面镍铬合金化层的耐海水好氧菌腐蚀性能

目的 揭示弧辉等离子体镍铬共渗处理对Q235碳钢表面成分、结构和耐海水好氧菌腐蚀性能的影响。方法 采用弧辉等离子体渗镀技术在Q235碳钢表面制备镍铬合金化层。利用X射线衍射仪（XRD）和扫描电子显微镜（SEM）对镍铬合金化层的相组成、表面形貌和截面元素分布进行分析。利用电化学测试技术,测试并分析镍铬合金化层在海水好氧菌中的腐蚀电化学行为。结果 Q235碳钢经弧辉等离子体镍铬共渗后,表面形成了一层厚度约为50μm的镍铬合金化层,合金化层的物相为Ni2.9Cr0.7Fe0.36固溶体。在好氧菌中浸泡时,Q235碳钢表面形成了生物腐蚀膜,腐蚀膜的存在使Q235碳钢的腐蚀电位负移,局部耐蚀性降低。与Q235碳钢相比,镍铬合金化层的表面能降低,表面接触角达到111°。镍铬合金化层在好氧菌中浸泡11 d后,仅在很少的局部位置观察到细菌附着,未观察到明显的腐蚀膜。结论 Q235碳钢在好氧菌中浸泡时腐蚀严重,浸泡5 d后就在其表面形成了一层由腐蚀产物、培养基和细菌形成的腐蚀产物膜,腐蚀产物对生物膜的形成有一定的促进作用。镍铬合金化层降低了Q235碳钢表面的表面能,阻碍生物膜底膜的形成,同时形成的钝化层...     

铸钢件表面铸渗结晶硅复合层的探讨

研究了不同铸渗工艺对铸钢件表面铸渗硅复合层厚度和质量的影响。采用扫描电子显微镜（SEM）、X射线能谱（EDS）及显微硬度仪等分析手段，阐述了该铸钢件表面铸渗硅复合层的微观成分、组织及性能特点。结果表明，钢水的浇注温度为1580℃左右时，铸钢件表面可以得到厚度为0.6-2．8mm并且表面质量较好的铸渗硅复合层。另外渗硅层与母材铸钢的界面为机械结合状态。     

NaCl和SO2在A3钢初期大气腐蚀中的协同效应

研究了在25℃，相对湿度为80%的条件下，NaCl和低浓度SO2的协同效应对A3钢初期大气腐蚀行为的影响，分析了该条件下A3钢的初期大气腐蚀动力学，证实了NaCl和低浓度SO2的协效应导致腐蚀明显加剧，腐蚀失重远大于两者各自存在时引起的腐蚀，同时应用扫描电镜（SEM/EDAX），X射线衍射（XRD）和Fourier变换红外光谱（FTIR）对A3钢表面形貌和腐蚀产物进行了分析，阐述了NaCl和SO2协同效应的腐蚀机理。     

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).     

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.     

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.     

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。