Co-15Ce合金在800℃不同硫压下的硫化

研究了含15wt%Ce的Co-Ce合金在800℃、H2-H2S气体中的硫化腐蚀行为,硫分压分别为10-2Pa及10-3Pa.Co-15Ce合金在800℃硫压为10-2Pa时的腐蚀速度很快,几乎与纯Co相当,而在硫压为10-3Pa时,因其硫压在硫化钴的平衡分解压之下,故其腐蚀速度很慢.该合金硫化腐蚀后形成复杂的腐蚀产物膜,在硫压为10-2Pa时其腐蚀产物膜的最外层为纯Co的硫化物层,其下为Ce的硫化物与Co的硫化物的混合物层,内层为Ce的硫化物与金属Co的混合物层;在硫压为10-3Pa时其腐蚀产物膜仅为Ce     

应变速率对X80管线钢在库尔勒土壤环境中应力腐蚀开裂的影响

利用慢应变速率拉伸试验(SSRT)、动电位扫描及扫描电镜(SEM)技术研究了X80管线钢在库尔勒模拟溶液中应力腐蚀开裂(SCC)行为.结果表明,随着应变速率的增加,X80管线钢在模拟溶液中的腐蚀速率先增大后减小.当应变速率为5×10-7/s时,试样腐蚀较为缓慢,此过程电化学腐蚀起决定性作用;当应变速率为5×10-6/s时,试样的腐蚀情况最为严重,此时力学作用占主导地位.     

P110钢冲刷腐蚀预测模型的构建及其机理研究

目的 探究高温高压环境下P110钢在不同冲刷速度和角度下的腐蚀行为规律,揭示其冲刷腐蚀机理,建立腐蚀预测模型,以期指导油气田材料腐蚀防护与腐蚀预测。方法 采用电化学工作站和高温高压反应釜,开展高温高压冲刷腐蚀实验。采用金相显微镜、扫描电子显微镜、X射线衍射仪等对冲刷腐蚀前后材料的微观组织结构、化学成分及物相进行表征。此外,通过调研文献数据,基于随机森林(Random Forest,RF)算法构建了P110钢的冲刷腐蚀预测模型,并开展了预测准确性研究。结果 在3 m/s的冲刷速度下,随着冲刷角度的增加,自腐蚀电流密度由30°的2.19×10⁻⁴ A/cm²降低到90°的1.449×10⁻⁴ A/cm²。在30°的冲刷角下,随着冲刷速度的增加,自腐蚀电流密度由0 m/s的6.30×10⁻⁵ A/cm²增加到3 m/s的2.19×10⁻⁴ A/cm²。腐蚀产物具有双层膜结构,外层主要由FeCO3组成,内层主要为Fe2O3。腐蚀预测模型分析结果表明:温度对P110钢的腐蚀速率影响程度最大,其次是CO2和冲刷速度。结论 在高温高压环境下,P110钢能够产生Fe2O3和FeCO3的双层腐蚀产物膜,随着冲刷速度的增加和角度的降低,腐蚀产物膜完整性破坏,腐蚀加剧。腐蚀预测模型具有良好的性能,能够有效预测腐蚀速率。     

石油化工钢制压力容器的应力腐蚀行为研究

以石油化工304L不锈钢压力容器为研究对象,采用慢应变速率试验方法,研究了不同温度和腐蚀介质浓度下的应力腐蚀变化规律和断口特征。结果表明,当应变速率为1×10~(-6)s~(-1)时,随着温度的升高和NaOH浓度的增加,304L不锈钢压力容器的应力腐蚀敏感性增加;随着温度的升高,压力容器的腐蚀倾向越大,断裂特征已经逐渐从韧性断裂转为脆性断裂,尤其是当温度为280℃时已经发生了较为显著的应力腐蚀;随着腐蚀介质浓度的增加,压力容器断裂的时间不断缩短。     

Co基合金在Na2SO4盐膜下的热腐蚀行为

研究了Co-10Cr、Co-25Cr和Co-10Cr-5Al合金涂敷Na2SO4盐膜后在900℃空气中的热腐蚀行为.结果显示,Co-10Cr合金的腐蚀增重最大,Co-10Cr-5Al的腐蚀增重其次,Co-25Cr合金腐蚀增重最少,抗热腐蚀性能最好.Co-10Cr合金腐蚀膜可分为3层,外层是CoO,中间层是Cr2O3,内层有少量的Cr2S3.Co-10Cr-5Al合金腐蚀膜可分为3层,外层是CoO,中间层是Cr2O3和Al2O3,内腐蚀区有Cr和Al的硫化物.Co-25Cr合金外层是CoO和Cr2O3,内层是单一的Cr2O3,无明显的内硫化现象.     

力学与电化学作用下X80钢焊接接头SCC行为分析

采用动电位扫描技术及慢应变速率拉伸试验(slow strain rate test, SSRT)研究了X80钢焊接接头在库尔勒模拟溶液中应力腐蚀开裂(stress corrosion cracking, SCC)行为,并利用扫描电镜(scanning electron microscope, SEM)对不同应变速率下试样断口形貌进行表征.结果表明,随着应变速率的增加,X80钢焊接接头的腐蚀速率则呈现持续增大的趋势.当应变速率为1×10-5/s时,试样的腐蚀情况最为严重. X80钢焊接接头在不同应变速率下的腐蚀机制是由电化学-力学交互作用共同决定的.试样发生应力腐蚀后断裂于焊缝处,这是由于焊接过程导致焊缝晶格存在大量的缺陷,使得晶格活性较高所致.     

TA32钛合金板材的超塑性能研究

研究了真空环境中TA32钛合金板材在温度950℃、应变速率5. 32×10~(-4)～2. 08×10~(-2)s~(-1)条件下的超塑性变形行为。结果表明,在不同应变速率条件下,合金的流变应力曲线特征和显微组织演变显著不同。在应变速率较低(5. 32×10~(-4)～3. 33×10~(-3)s~(-1))条件下,拉伸真应力-真应变曲线呈传统超塑变形的稳态流动特征,变形后的合金中初生α相晶粒尺寸较大;在高应变速率(8. 31×10~(-3)s~(-1)～2. 08×10~(-2)s~(-1))条件下,拉伸真应力-真应变曲线中流变应力增大到峰值后快速单调递减直至试样断裂,合金变形过程中初生α相发生动态再结晶,晶粒尺寸较低应变速率条件下显著细化。950℃时,TA32钛合金板材均具有超塑性变形能力,超塑性延伸率在145%～519%之间;当应变速率为5. 32×10~(-4)s~(-1)时,具有最佳的超塑性,拉伸延伸率可达519%。断裂区形貌分析发现,TA32钛合金板材的超塑性断裂模式为空洞聚集-连接-长大型断裂。     

Q235钢在氧化性含Cl气氛中的高温腐蚀行为

研究了500和600℃下N2-0.26％HCl-1.6％O2-3.2％CO2混合气体中Q235钢的高温腐蚀行为.结果表明,在两个温度下Q235钢均出现了明显的腐蚀增重.随着温度的升高,腐蚀速率迅速增加.在两个温度下形成的氧化膜比较类似,分层明显,外层为较厚的Fe2O3层,内层为Fe3O4.大部分氧化膜表面出现了剥落和起...     

油气田腐蚀环境中N80钢和3Cr钢的腐蚀行为

采用失重法、X射线衍射法、扫描电镜观察及能谱分析等方法比较研究了N80钢和3Cr钢在模拟胜利油田某油井腐蚀环境中的腐蚀行为。结果表明:在试验条件下,N80钢和3Cr钢的腐蚀速率随腐蚀时间的延长均呈现先急剧降低后缓慢降低的趋势,N80钢的腐蚀速率明显高于3Cr钢的;腐蚀360h后,N80钢表面形成的腐蚀产物膜呈双层结构,XRD测试结果表明两层产物膜均由FeCO_3构成,后期沉淀形成的外层膜较为疏松,原位形成的内层膜致密完整,计算得到双层产物膜的平均密度为1.54g/cm~3;3Cr钢表面形成的腐蚀产物膜为致密完整的单层膜结构,由FeCO_3和Cr(OH)_3构成,产物膜平均密度为2.571g/cm~3。3Cr钢表面形成的腐蚀产物膜的保护性远远优于N80钢表面形成的腐蚀产物膜的。     

耐硫化氢腐蚀钢在硫化氢介质中的腐蚀行为

采用电化学方法、X射线光电子能谱仪和扫描电镜等方法对抗硫化氢腐蚀的套管钢BG110S在含饱和硫化氢的NACE溶液中的腐蚀行为进行了研究。结果表明:耐硫化氢腐蚀钢在25℃含饱和硫化氢的NACE溶液中与硫化氢发生了反应,形成双层结构的腐蚀产物膜,外层是以四方晶系FeS为主的腐蚀产物膜,内层为铬、铜等合金元素硫化物的腐蚀产物膜;腐蚀产物膜能够阻挡基体合金元素与硫化氢发生进一步的腐蚀反应,降低了氢原子渗透量,从而提高了耐硫化氢腐蚀钢的抗硫化氢腐蚀的性能。     

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。