45钢与钨钴硬质合金的钎焊组织与性能

为实现中碳钢和硬质合金的高效优质钎焊,以Cu-Zn钎料对硬质合金和中碳钢进行了感应钎焊。结果表明,黄铜钎料可以使硬质合金和中碳钢形成良好的钎焊接头;分析了钎焊接头界面组织,接头区由α铜、Fe-Cu-Zn三元反应层构成;维氏硬度测试结果表明,因感应加热淬火效应,焊接后硬质合金显微硬度有显著增加;对感应钎焊的打磨头进行了电镀Cr处理,铬镀层提高了打磨头的耐蚀性和美观程度。     

钨铜/铍青铜异质钎焊界面组织与性能

采用BAg56CuZnSn,BAg50ZnCdCuNi和BAg49ZnCuMnNi银钎料实施了钨铜合金/铍青铜异质材料接头的感应钎焊连接,研究了其钎焊界面组织与力学性能.结果表明,3种银钎料均能获得完好界面钎焊接头,钎料与钨铜和铍青铜形成较好冶金结合.钎料与铍青铜界面冶金结合充分,形成明显互扩散区.钎料与钨铜钎焊界面清晰,且钎料向钨铜近界面区域形成明显扩散渗入现象.强度测试表明,BAg49ZnCuMnNi钎焊接头强度最高,达到250 MPa,接头断裂均发生在钨铜侧钎焊界面.分析表明,钎料向钨铜渗入明显促进界面结合,钎料中添加镍,由于镍与钨的扩散互溶进一步提高界面冶金结合,Mn元素添加明显细化钎缝晶粒,接头强度显著提升.     

钎后扩散对AgCu28钎料真空钎焊紫铜接头组织和性能的影响

为了研究钎后扩散处理对Ag Cu28共晶钎料真空钎焊紫铜接头组织和性能的影响,进行了800℃钎焊无扩散、钎后770℃扩散45 min的薄壁管-板接头钎焊试验。利用扫描电镜、能谱分析、显微硬度等分析测试手段,对比分析了两种钎焊接头的组织和性能。结果显示:钎焊接头组织为银基、铜基固溶体及铜银二元共晶,钎后扩散处理的钎料中心区较未扩散的明显变窄,且界面区呈波形生长,固溶体增多,铜银二元共晶逐渐减少。从母材区、界面区到钎料中心区,显微硬度依次减小,且经过钎后扩散处理,钎料中心区显微硬度增加。     

不锈钢/铜感应钎焊接头组织和力学性能研究

采用Cu-Zn钎料感应钎焊不锈钢/铜接头,并利用金相显微镜、扫描电镜、显微硬度计和万能拉伸试验机对钎焊接头的显微组织和力学性能进行了分析。结果显示:钎焊后钎料/不锈钢界面的形貌由一层化合物、沿晶界生长的针状金属间化合物及向晶内生长的二次树枝晶金属间化合物组成。在远离界面的钎料内部还有金属间化合物沿晶界析出。近钎缝区的铜显微硬度明显降低,不锈钢侧硬度降低不明显,钎缝的显微硬度明显增加,这是由于较快的冷却速度导致黄铜钎料出现大量的Cu Zn相。钎焊接头拉伸断口位于远离钎缝的铜管上,抗拉强度达到260 MPa,显示出良好的力学性能。     

采用Ni基钎料和Cu中间层真空钎焊W/CuCrZr的接头组织和性能研究

以20μm厚的纯Cu片作为中间层,采用20μm厚的非晶态Ni基钎料箔在在900、930、950℃下保温10min真空钎焊W和CuCrZr合金。采用SEM和EDS分析了钎焊接头的界面形貌,检测钎焊接头的剪切强度及显微硬度。结果表明,中间层Cu与母材CuCrZr合金一侧界面结合良好,在CuCrZr合金一侧形成了钎焊热影响区;钎料与W母材界面处形成了反应层,在W母材侧有微裂纹。随着钎焊温度的升高,W侧裂纹增多,造成接头性能的迅速恶化。W和CuCrZr的钎焊温度最好控制在930℃以下。以纯Cu片为中间层,采用Ni基钎料钎焊W和CuCrZr的过程,实质上是Ni与Cu、W互相扩散并反应生成化合物层和固溶体的过程。钎焊接头的最佳剪切强度为144MPa,断裂主要发生在W母材及W与反应层之间的界面。钎缝区域的显微硬度随钎焊温度的升高而降低,CuCrZr合金焊接热影响区的硬度高于其母材。     

ZnAl15夹层AZ31B/Cu扩散钎焊接头组织与性能的研究

以ZnAl15钎料为中间夹层,对AZ31B镁合金与铜在不同温度下进行扩散钎焊。通过电子显微镜观察、能谱成分分析、显微硬度测定、剪切试验等测试方法,研究了焊接温度对焊接接头界面结合区显微组织、元素分布、显微硬度和剪切强度的影响规律。结果表明,采用ZnAl15夹层可以获得冶金结合良好的扩散钎焊接头。界面扩散区由铜侧扩散层、块状化合物层、共晶组织层以及镁基体渗透层三部分组成。在480~500℃,保温10min条件下,随着焊接温度的升高焊缝的宽度增加。在480~500℃,保温20min条件下,接头界面区的显微硬度均呈现两边低中间高的分布规律。随着温度的升高,接头的显微硬度不断增大,而剪切强度呈现先增再减的变化趋势;490℃时接头的剪切强度达到最大,约为64MPa。     

高强韧CuZnNiMn纽扣钎料钎焊截齿接头组织与性能

针对采煤、掘进机械用截齿,采用短流程方式制备了Cu-Zn-Ni-Mn纽扣型钎料.使用制备的纽扣型钎料,采用高频感应方式完成了实际产品的焊接.焊后分别对焊接接头的宏观形貌、剪切性能、剪切断口形貌、钎焊界面组织及成分进行分析.结果表明,制备的纽扣型钎料能够良好的润湿钢基体和硬质合金,钎焊填缝率达到100%;钎焊接头剪切强度260 MPa以上,剪切形貌为典型的韧窝状韧性断裂.在钢基体-钎料侧,Fe原子与Co原子出现长程扩散,形成Fe基固溶体和Fe-Co-Ni单相固溶体,钎料-硬质合金侧界面的强度依靠钎料向硬质合金内部的扩散与Co元素的固溶获得.     

不锈钢方管套接接头电子束钎焊微观组织分析

选用合理的电子束钎焊工艺参数,获得了良好的钎焊接头.用扫描电镜和能谱分析仪对钎焊接头的显微组织进行了分析.结果表明,钎料区主要是固溶体组织;母材区除了奥氏体组织外,存在铜元素的扩散.     

铝和Q235镀锌钢搭接GMAW熔-钎焊接头组织分析

本文以AI-5Si焊丝为填充材料,研究了采用GMAW焊实现Q235钢和5A02铝合金熔一钎焊连接的可行性,分析了接头区显微组织和缺陷。结果表明,采用GMAW焊可以实现Q235钢和5A02铝合金的良好连接,并在钢与钎料连接界面处产生了5um左右的金属间化合物层,钢与钎料连接界面处显微硬度可达192．6MPa。当选择工艺参数不当时,在熔一钎焊接头内发现了气孔、未钎透及热裂纹等缺陷,未钎透和热裂纹主要分布在焊接接头根部,焊接接头根部成为钢铝熔－钎焊连接的一个薄弱区。     

钢/铜火焰钎焊接头组织和性能研究

采用Cu-Zn系黄铜钎料火焰钎焊钢/铜接头,并利用扫描电镜、显微硬度计和万能拉伸试验机对钎焊接头的显微组织和力学性能进行了分析评估。结果显示:使用含有Si的黄铜钎料钎焊后,钎料/钢界面会出现薄层Fe-Si金属间化合物,并且由于Fe-Si金属间化合物的脆性,导致此处出现微裂纹。由于黄铜钎料的熔化温度较高,钎焊过程中近焊缝的铜管发生再结晶退火,其显微硬度明显降低,强度也相应地降低。但根据以往经验,该接头在家用空调的服役条件下不会发生问题。试样的拉伸断裂位置在远离钎缝的铜管上,抗拉强度达到235 MPa,显示出良好的力学性能。     

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。