双辊连铸不锈钢薄带内部质量缺陷的研究

对双辊薄带连铸机生产的2 mm厚不锈钢薄带内部质量进行了研究,发现主要问题是存在于薄带柱状晶区和等轴晶区之间的疏松和裂纹.双辊连铸薄带内部缺陷易发区域金相观察和EBSD取向分析结果表明,不锈钢薄带等轴晶和柱状晶之间细晶区是折断的树枝晶碎块形成的,同时验证了等轴晶区的半固态特性.并从半固态钢液铸轧的角度探讨了内部缺陷形成过程.     

双辊薄带连铸工艺的研究现状与展望

主要介绍了有关薄带连铸的工艺及其数值模拟的历史和最新发展。对比分析了薄带连铸的凝固行为和组织形貌、力学性能，提出了薄带连铸过程中存在的尚待解决的工艺问题，并列出了一些影响薄带表面质量的工艺参数。     

镁合金双辊薄带连铸技术的研究现状及进展

双辊薄带连铸技术作为一种有潜力的镁合金板带材生产技术,其研究开发正受到国内外的关注。本文总结了镁合金双辊薄带连铸技术的研究概况,尤其是镁合金双辊薄带连铸工艺开发、薄带组织和性能研究以及薄带凝固过程的数值模拟等方面取得的进展,指出了该技术目前还存在的问题,并对今后的发展进行了展望。     

AISI304不锈钢双辊连铸薄带的组织性能

测量了双辊薄带连铸机生产的AISI304连铸薄带的力学性能,采用光学显微镜、扫描电镜和透射电镜观察了连铸薄带的微观组织结构,分析了微观组织结构对性能的影响.结果表明,连铸薄带内部为铸态组织,二次枝晶间距平均值为6.7μm,细小的铸态组织决定了薄带的最终组织细化和成分均匀;快速冷却有助于形成球形夹杂物,直径500～700 nm,较小的球形夹杂物能够钉扎位错;连铸薄带内析出粒子的直径20～100 nm,这种微小析出能够产生沉淀强化作用;薄带组织中大量位错、层错和孪晶的存在一定程度提高了连铸薄带力学性能.     

连铸AISI304不锈钢薄带夹杂物的研究

采用大样电解方法研究了双辊连铸工艺生产的AISI304薄带内大型夹杂物的类型和数量，运用带有能谱的扫描电子显微镜分析了薄带内部细小的夹杂物类型。结果表明，连铸薄带内大型夹杂物的数量很少，只占薄带总量的0．0015％，大型夹杂物类型多为氧化物；薄带内有更细小的氧化物类夹杂物和MnS夹杂物。大型夹杂物对薄带性能的不良影响较小，连铸薄带的性能较好。     

东大RAL承担的钢铁联合基金重点项目取得重要研究进展

<正>薄带连铸无取向电工钢具有高磁感的独特优势,然而薄带连铸情况下无取向电工钢铁损的影响因素及其物理冶金机理尚不十分明确。东大RAL承担的钢铁联合基金重点项目"凝固、冷却及热处理一体化柔性调控无取向硅钢夹杂物与析出物的基础研究",围绕双辊薄带连铸及后续轧制、热处理流程,针对无取向硅钢中的第二相粒子的析出与调控以及     

稀土Ce对薄带连铸无取向6.5%Si钢组织、高温拉伸性能和断裂模式的影响

研究了Ce元素对薄带连铸无取向6.5%Si钢凝固组织、有序相、高温拉伸性能和断裂模式的影响。结果表明，添加Ce可以在薄带连铸过程中形成高熔点Ce₂O_2.5S和Ce₄O₄S₃，促进钢液异质形核，细化铸带凝固组织。Ce对有序相变无明显影响，铸带有序度由高至低所对应的拉伸温度分别为650、400和800℃。随拉伸温度提高，铸带的屈服强度与抗拉强度降低，断后延伸率提高。当拉伸温度高于500℃，Ce元素的钢液净化和凝固组织细化作用有助于提高晶界强度，避免沿晶断裂。铸带在拉伸过程中发生动态回复和再结晶，最终发生韧性断裂，断后延伸率得到显著提高。研究结果证实，稀土处理可以作为薄带连铸无取向6.5%Si钢增塑的一种有效途径。     

双辊法薄带连铸空冷区传热过程计算机模拟

本文叙述了双辊法薄带连铸空冷区传热过程数学模型的建立,并初步验证了它的可靠性,依此计算了铸带在空冷区的温度变化规律,探讨了冷却强度对铸带温度分布的影响。     

热处理工艺对冷轧TRIP800钢组织与性能的影响

利用电子背散射衍射技术(EBSD)技术分析了两种不同热处理工艺下的TRIP800钢板取向分布、晶粒角度、显微织构与残余奥氏体的分布及其稳定性,并结合试验钢的力学性能进行了讨论.研究表明:两类试验退火钢的晶粒没有优势的取向分布,呈现较弱的织构;面心立方晶粒中的取向以{001}<100>与{011}<100>较多;残余奥氏体大多以分布在晶界上为主,但拉伸断裂后基本上消失,即产生了相变诱导塑性(TRIP)效应,而体心立方晶粒内部的残余奥氏体相对稳定,断裂后还有部分稳定的存在.     

再结晶退火4J6合金薄带的微观组织特征

对变形量为40%,厚度为1.8mm的冷轧4J6合金薄带施以不同温度相同保温时间的退火处理,采用金相组织观察,电子背散射衍射(EBSD)实验手段,研究了不同温度退火条件下,冷轧4J6合金薄带的显微组织和主要织构的演变规律以及晶界的取向差分布特征。结果表明,随着退火温度的增加,小角晶界的取向差逐渐减小,晶界的取向差主要分布在55°～60°之间;高斯织构及黄铜织构所占比例逐渐减小,<110>//RD织构逐渐增加。     

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。