消失模铸造充型过程数值模拟

运用PROCAST软件对板形铸钢件的消失模充型过程进行了数值模拟。考察了阶梯式浇注系统的充型顺序以及底注式浇注系统的充型形态，另外研究了底注式浇注系统的浇注速度对缺陷形成的影响。模拟结果表明，消失模铸造中，金属液优先从阶梯式浇注系统的上层内浇道充型，充型前沿流动紊乱，铸件容易出现气孔或夹渣；对于底注式浇注系统，充型前沿的流动相对平稳，但过快的浇注速度同样会导致气孔或夹渣缺陷。     

机床床身砂型铸造充型速度误差仿真研究

砂型铸造机床床身过程中,充型速度控制不当会使铸件表面产生变形和裂纹现象,导致机床床身综合性能下降。采用PLC控制金属液的充型速度,可实现充型速度控制误差的最小化。分析了机床床身砂型铸造的整个工艺流程,给出铸造工艺流程图。构造铸件充型流体计算方程式,给出PLC控制充型速度原理图,通过MATLAB软件对充型速度进行误差仿真。同时,与PI控制仿真结果进行对比和分析。结果表明,采取PLC控制机床床身砂型铸造充型速度,误差较小,充型速度稳定;采取PI控制机床床身砂型铸造充型速度,误差较大,充型速度不稳定。采用PLC控制砂型铸造金属液体充型速度,能够降低充型速度的误差,避免铸件表面应力集中,提高机床床身铸件表面质量。     

横向翻转浇注工艺铸造耐压外壳铝合金铸件

从铸造工艺、工装设计上进行改进创新,采用横向翻转浇注工艺铸造耐压外壳铸件。铸件在凝固过程中能从冒口不断地得到液态金属的补充,实现定向凝固。减少铝液二次氧化带来的夹渣,使铝液充型过程平稳,不易发生紊流。解决了铸件法兰密封面弥散性针孔和铸件轴密封处及凸台因壁厚不均产生缩松造成气密性差的问题。在实际铸造过程中通过对模具预热温度、合金浇注温度、翻转速度进行控制,提高了铸件整体质量。通过几年批量生产验证,一次检漏合格率达到99．8％。     

铝锭铸造免打渣技术的研究应用

铝电解生产中,铝锭铸造过程需要人工打渣.铝液从混合炉流向铸模的过程中因落差较大,落差处铝液的流动状态发生突变造成铝液氧化、铝渣增加.减少铝液的氧化,必须采取技术措施减少铝液的翻滚.介绍了一种新技术,将浇注线重新设计,使浇注线几乎成为封闭式的,流动的金属液最大限度地减少与空气接触.这种浇注方式使铝液在浇注转注过程中的氧化得到降低,使铝渣大幅减少,达到可以忽略的程度,从而实现免打渣,获得可观的经济效益和社会安全效益.     

基于铸件斜面及螺旋面结构特征的砂型铸造浇注系统优化设计

当铸件具有斜面或螺旋面的结构特征时,可利用自身结构特征设置出类似蛇型或鹅颈型的浇注系统,蛇型或鹅颈型的浇注系统可增加流动阻力,降低流速,减少和防止液态金属的冲击、飞溅和氧化。分析比较了几种具有斜面或螺旋面结构特征铸件的典型浇注系统设置方案。结果表明,通过利用金属液在斜面及螺旋面平稳缓流的特点,在铸件的斜面或者螺旋面设置浇注系统,可以使液体金属的充填既具有底注式浇注系统的充型平稳、金属氧化轻、对型（芯）冲击小,有利于排气、充型快和挡渣能力强的优点,又改善了底注式浇注系统的造型复杂、金属消耗量大的缺点。     

消失模铸造充型速度和流动前沿温度的数值模拟研究

采用数值模拟方法,通过模拟板形灰铸铁件的消失模铸造充型过程,分析了各种工艺因素对充型过程中金属液前沿的流动速度和温度的影响规律.结果表明,液态金属充型速度随浇注温度、负压度和涂层透气性的增大而增大,随模样密度和涂层厚度的增大而减小;金属液流动前沿温度随模样密度和涂层厚度的增大而下降,而随负压度的增大而提高.     

阀体砂型铸造充型凝固过程数值模拟研究

由于阀体零件结构复杂,砂型铸造阀体时,浇注系统和工艺参数不当容易导致铸件出现缩松、缩孔等缺陷。采用Pro CAST软件对典型阀体砂型铸造过程进行数值模拟,研究了金属液充型和凝固过程。分析了缺陷产生的原因,改进了浇注工艺方案,提高了铸件的质量和合格率。     

大型铸铝件铸造工艺有限元分析与优化

先对大型铸铝件设计两种浇冒口系统方案,然后利用有限元数值模拟方法对其充型流场及凝固过程温度场进行耦合分析,预测铸件铸造过程中缩孔缩松缺陷的产生,并对不同浇注速度条件下铸件的充型流场和充型初期流动前沿进行分析,优化出合理的浇冒口系统设计方案以及浇注速度,最终得到更为可行的铸造工艺方案.     

铝合金正时罩盖压铸模浇注系统优化设计

针对铝合金正时罩盖进行铸件结构分析,设计了两种不同方向进料的浇注系统方案,运用Anycasting铸造模拟软件对两种方案的充型过程进行模拟。通过观察两种方案的充型流态、表面缺陷分布位置,预测金属液流动过程产生的气孔、氧化夹渣等缺陷。对比分析各方案中缺陷对铸件各功能区域的影响及严重程度,筛选出最优方案,并根据模拟结果优化最终浇注系统方案,满足铸件质量要求。     

优化零件结构采用金属型旋转浇注铸件

从优化零件结构、铸造工艺、工装设计上进行改进创新,借鉴西欧和日本先进经验,采用金属型、铁芯、旋转浇注铸造工艺,减少缩松、铝液二次氧化带来的夹渣,使铝液充型过程平稳,不易发生紊流,解决了铸件法兰密封面弥散性针孔和铸件因壁厚不均产生缩松造成气密性差的问题。在实际铸造过程中通过对模具预热温度、合金浇注温度、旋转速度进行控制,提高了铸件整体品质。通过几年批量生产验证,一次检漏废品率不超过到3‰。     

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。