碳钢精铸件铸态脱碳的研究

利用金相，显微硬度和计算机图象分析等方法，研究了碳钢精铸件的铸态脱碳问题。文中还讨论了脱碳温度范围及防止脱碳的工艺措施。     

铸渗硼层显微组织观察

利用铸渗硼工艺在铸件的表面形成一层硬度较高耐磨性较好的硼化物层,通过对铸渗硼层的显微组织进行分析,发现在铸渗硼剂中加入铜粉可使硼化物层致密,并使铸渗硼层内缩孔、气孔等缺陷较少。同时分析了合金粉剂粒度对组织的影响和铸渗硼层中的硼化物的生长方向。     

铜及稀土元素对中碳钢铸渗层组织性能的影响

在采用涂覆法使中碳钢铸件表面铸渗铬、硼和碳,形成硬度较高的合金化层的基础上,再在渗剂中分别添加一定量铜和稀土元素,来研究铜和稀土对铸渗层组织和性能的影响.实验证明,加入铜或稀土元素的渗层表面质量得到了明显的改善,渗层硬度提高,并且,晶粒细化的效果比较突出.     

中碳钢表面铸渗合金化层组织和性能研究

采用涂料法在铸件表面铸渗硼、铬和碳等形成硬度较高的表面合金化层,研究了涂料配比对铸件表面合金化层组织和性能的影响.实验证明,所形成的合金化层由三部分组成:亚共晶层、共析层和基体;随着涂料中铬和碳含量的增加,合金化层的厚度也随之增加,而且硬度也整体提高.     

稀土在球铁铸渗钒钛合金中的应用

在球铁铸渗钒、钛合金时,用稀土元素作催渗剂,可使铸渗件表面的渗层深度由0.35mm提高到0.55mm,同时使渗层中合金碳化物的数量增多,粒度得到细化,从而提高了铸态球铁铸件表面的耐磨性。     

铸铁铸态渗硼的研究

本文探讨了铸铁在铸造条件下进行涂料渗硼的工艺。研究了铸渗硼后的金属显微组织、相结构、硬度以及硼、碳的分布。结果表明,在铸型表面涂以B4C为主的涂料,铸件表面可获一层含硼共晶层,其组织特征与白口铁相似。与基体相比,其硬度明显提高(HV0.05＝1400~1500),该层的组织和深度要受工艺因素(如浇注温度、冷却速度等)的影响。该工艺操作方便、成本低、周期短、节省能耗。渗硼铸铁可作耐磨材料用。     

稀土氮碳硼共渗对45钢疲劳性能的影响

研究了稀土氮碳硼共渗对45钢疲劳性能的影响。结果表明，稀土氮碳硼共渗处理后，45钢疲劳寿命显著提高，裂纹形成延迟，裂纹扩展速度降低。表面出现残余压应力和表面硬度提高是稀土氮碳硼共渗处理改善45钢疲劳性能的主要原因。     

影响扩散的新因素

在进行工件渗硼试验中，发现了一种反常现象。渗碳后再进行渗硼，虽然工件表面含碳量大为增加，但渗硼速度不但不减，反而显著增大。此后又发现低温氮碳共渗亦能提高钢件的渗硼速度，更可贵的是氮碳共渗不仅能提高渗硼速度．而且还可以显著提高钢件渗金属的速度。     

表面铸渗硼组织中奥氏体转变产物

铸渗硼法制备铸造表面复合材料简单易行,是提高铸件表面耐磨、抗蚀、耐高温等性能的有效途径。铸渗硼技术的开发和应用研究较多［１～５］,但对表层组织结构的报道较少。本文对铸渗硼组织中奥氏体冷却转变产物进行分析。１　试验方法基体材料为ＨＴ２００。合金预制块由粒度为１００目的硼铁和工业纯一级品硼酸按质量比为７∶３组成。硼铁的成分（ｗ,％）为：Ｂ２３－１３,Ｓｉ３－６２,Ａｌ１－７４,Ｐ０－００６,Ｃ０－０４,Ｆｅ余量。混合物在一定大压力及３５０℃下保温后,获得具有一定孔隙度的合金预制块。预制块置于砂型的侧…     

B（C2H5）3等离子辅助渗硼的研究

对新型渗硼剂Ｂ（Ｃ２Ｈ５）３的渗硼工艺进行了研究。结果表明：在正常渗硼工艺条件下,基体表面没有形成连续致密的渗硼层,而是形成了一层数μｍ厚的硼碳层;在间歇渗硼工艺条件下,基体表面形成了一层致密的渗硼层,这是因为通过溅射消除了在渗硼过程中沉积在基体表面的硼碳层,使硼原子在渗硼时能无阻碍地向基体内部扩散的缘故     

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。