Ag-Cu-Ti钎料钎焊金刚石的界面微观组织分析

在真空炉中采用Ag-Cu-Ti钎料对金刚石磨粒进行了真空钎焊试验,实现了金刚石与钢基体的高强度连接.采用SEM对金刚石与钎料界面、金刚石表面碳化物形貌进行了观察分析,采用EDS分析了金刚石与钎料界面的成分变化,采用Raman对焊后的金刚石结构进行了分析.结果表明,Ag-Cu-Ti钎料中的Ti元素在界面处发生偏析,并在金刚石表面生成尺寸小于1 μm块状TiC,金刚石在焊接过程的高温中没有发生石墨化,最后在界面上形成了金刚石/TiC/钎料/钢基体的梯度结合层.     

银基钎料钎焊金刚石的界面结构及TiC生长机制

在合适的工艺下,采用Ag-Cu-Ti钎料实现了金刚石与钢基体的高强度连接,并剖析了Ag-Cu-Ti钎料与金刚石的界面微区结构.通过对界面处的成分分布和深腐蚀后碳化物TiC形貌的观察,分析了Ti的作用机理、新生化合物TiC的形貌及生长规律.结果表明:在一定的条件下,Ti元素与组成金刚石的碳元素发生反应形成TiC层;碳化物层使钎料与金刚石之间产生冶金结合,并在其界面上形成了金刚石/TiC/钎料/钢基体的梯度结合层.     

含钛钎料钎焊金刚石的微结构对比分析

采用Ag-Cu-Ti和Ti-Zr-Ni-Cu钎料分别对金刚石磨料进行钎焊,实现了金刚石与钢基体的牢固连接。采用SEM、EDS等手段对焊后试样进行测试分析,结果表明:Ag-Cu-Ti焊后金刚石表面生成少量不连续块状TiC;Ti-Zr-Ni-Cu钎料焊后生成较多的连续鹅卵石的TiC。     

含钛钎料钎焊金刚石的微结构对比分析

采用Ag-Cu-Ti和Ti-Zr-Ni-Cu钎料分别对金刚石磨料进行钎焊，实现了金刚石与钢基体的牢固连接。采用SEM、EDS等手段对焊后试样进行测试分析，结果表明：Ag-Cu-Ti焊后金刚石表面生成少量不连续块状TiC；Ti-Zr-Ni-Cu钎料焊后生成较多的连续鹅卵石的TiC。     

铜基钎料真空钎焊金刚石

采用铜基合金钎料,适当控制钎焊工艺,实现了金刚石与钢基体的高强度连接.借助扫描电镜(SEM)、X射线能谱(EDS)、X射线衍射(XRD)分析了真空加热条件下,对铜基合金钎料与金刚石之间的界面反应,钎焊面进行了表面形貌和结构分析.探讨了钎料与金刚右界面处碳化物的形成机理.阐明了在钎焊过程中Ti元素在金刚石界面形成富Ti层并与金刚石表面的C元素反应生成TiC、SnTi C是实现合金层与金刚石有较高结合强度的主要因素.钎料与钢基体在钎焊温度下发生组元间相互扩散,形成了固溶体及其化合物,从而实现钎料与钢基体的高强度结合,并对一系列铜基钎料进行了测试.     

真空钎焊金刚石界面碳化物的形貌

采用Ni-Cr、Ag-Cu-Ti和Ti-Zr-Ni-Cu等钎料分别对单晶金刚石与基体进行真空钎焊。SEM、EDS和XRD等分析结果表明,在一定的钎焊温度、时间及真空度下,金刚石与所有钎料均形成化学冶金结合,在不同钎料界面形成的碳化物的种类、数量和形貌分布却显著不同;Ni-Cr合金钎料在界面处形成片状的Cr3C2和针状Cr7C3;Ag-Cu-Ti钎料则生成不连续分布块状TiC,Ti-Zr-Ni-Cu生成的是呈鹅卵石状连续分布的TiC。     

激光钎焊金刚石磨粒界面微结构分析

采用Ni基合金钎料,在Ar气保护条件下,对金刚石磨粒进行了激光钎焊试验研究.采用扫描电镜(SEM)和能谱仪(EDS)及X射线衍射仪(XRD)对钎焊金刚石试样进行理化分析,探讨了钎料与金刚石界面处碳化物的形成机理.结果表明,激光钎焊过程中在金刚石表面附近形成的富Cr层与金刚石表面的C元素反应生成碳化物,在钢基体结合界面上Ni-Cr合金钎料和钢基体中的元素相互扩散形成化学冶金结合.     

Ag—Cu—Ti钎料中Ti元素在金刚石界面的特征

研究了金刚石钎焊接头中碳化物形成元素Ti与金刚石（或石墨）之间的相互作用行为。通过对接头界面处的成分分布和断口形貌观察,分析了Ti的作用机理、新生儿合物TiC的断口形及生长规律,结果表明：在一定的条件下,Ti元素与组成金刚石（或石墨）的碳元素发生反应形成TiC层;碳化物层使钎料与金刚石之间产生冶金结合;TiC与金刚石之间存在有明显的界面,TiC断口的微观表面形态呈韧窝状;在金刚石表面初始形成的TiC的生长方向与金刚石的晶向指数有关。     

基于Ag-Cu-Ti钎料的超高频感应连续钎焊金刚石界面结构及残余应力

采用Ag-Cu-Ti合金钎料,在不同的超高频感应连续钎焊工艺条件下实现了金刚石磨粒与大尺寸钢基体的连接。借助扫描电镜(SEM)对钎焊后的金刚石界面微观结构进行观察,采用Raman光谱对钎焊后金刚石的残余应力状态进行了测试分析。结果显示,超高频感应连续钎焊金刚石表面Ti C晶体的生成处于非平衡态的过程。随着扫描速度的变化,Ti C晶体呈现球状和岛状,偏离了理想的正八面体形态。钎料层内部出现富Cu枝晶组织,而在45#钢基体表层形成了马氏体组织。钎焊后的金刚石磨粒顶部受到残余压应力,最大值为500 MPa,磨粒底部受到残余拉应力,最大值为150 MPa,这种分布趋势与传统真空炉中钎焊方法获得的残余应力分布刚好相反。     

CVD金刚石膜的钎焊界面反应层及微结构

借助扫描电镜和电子探针,分析了金刚石与Ag-Cu-Ti活性钎料界面反应层的微观组织结构、界面新生化合物的形成机理以及焊接工艺条件对界面结构的影响,建立了钎焊接头界面结构物理模型.结果表明,在一定的钎焊工艺条件下,金刚石/钎料界面存在灰色的新生化合物TiC,与TiC相邻的是蜂窝状的TiCu相;接头断裂不仅仅发生在TiC相中,有时断裂也发生在TiCu层.钎焊加热温度、保温时间、钎料层的含Ti量对CVD金刚石厚膜与硬质合金的接头结构模型有重要影响.     

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。