石墨/紫铜间接钎焊接头的界面组织及力学性能

在950℃,30 min条件下,采用含活性元素Ti的Sn0.3Ag0.7Cu-x Ti(x=1.0,1.2,1.4,1.6,1.8,质量分数,%)金属粉末对石墨进行反应金属化,然后用Sn0.3Ag0.7Cu钎料在真空条件下实现了紫铜和石墨的间接钎焊.钎焊接头的典型界面结构为:紫铜/Cu3Sn/Cu6Sn5/b-Sn/Ti C/石墨.在反应金属化过程中金属化粉末中的Ti起到重要作用,而Ti含量对钎焊接头的界面组织和抗剪强度没有影响.随着钎焊温度升高,紫铜中越来越多的Cu溶解到液相钎料中反应生成Cu-Sn化合物,接头的抗剪强度有一定程度的提高.断口分析表明:接头主要在b-Sn层中断裂,并呈现韧性断裂.当Cu-Sn化合物充满整个钎缝(600℃),接头强度大幅提高,达到30 MPa,接头在石墨母材完全断裂.     

SiC_p/2024Al复合材料与SiC陶瓷的软钎焊

采用Sn3.0Ag0.7Cu钎料对表面电镀铜后的增强相体积为45%的SiC_p/2024Al复合材料和表面化学镀铜后的SiC陶瓷进行钎焊,利用扫描电镜、材料试验机等研究了钎焊接头的显微组织、剪切断口形貌以及钎焊保温时间对接头组织和性能的影响。结果表明:表面电镀铜后的SiC_p/2024Al复合材料能够实现与表面化学镀铜的SiC陶瓷的软钎焊,在260℃下保温0.5min能得到剪切强度为24MPa的接头,焊缝组织致密,钎料对电镀铜后的SiC_p/2024Al复合材料和化学镀铜后SiC陶瓷的润湿性都良好,断裂部位发生在铝基复合材料与电镀铜结合处以及电镀铜层较薄弱处。     

AgCu+nano-Al_2O_3复合钎料钎焊TC4合金与Al_2O_3陶瓷:界面结构及接头性能

通过向Ag Cu共晶钎料中添加nano-Al2O3增强相(2%,质量分数)并采用高能球磨的方法获得了Ag Cu+nano-Al2O3复合钎料(Ag Cu C钎料)。采用Ag Cu C钎料实现了TC4合金与Al2O3陶瓷的高质量钎焊连接,确定了TC4/Ag Cu C/Al2O3钎焊接头的典型界面组织结构为:TC4/α-Ti+Ti2Cu扩散层/Ti3Cu4层/Ag(s,s)+Ti3Cu4+Ti Cu/Ti3Cu4层/Ti3(Cu,Al)3O层/Al2O3。Nano-Al2O3的添加抑制了钎缝中连续的Ti-Cu化合物层的生长,同时在钎缝中形成了颗粒状Ti-Cu化合物相增强的Ag基复合材料,改善了钎焊接头的界面组织。随着钎焊温度的升高,各反应层厚度逐渐增加,颗粒状Ti-Cu化合物不断长大,Ag基复合材料组织逐渐细小。当钎焊温度T=920℃,保温时间t=10 min时接头抗剪强度达到最大为67.8 MPa,典型断口分析表明:压剪过程中,裂纹起源于钎角处并沿钎缝扩展后转入Al2O3陶瓷,最终在Al2O3陶瓷母材侧发生断裂。     

高纯氧化铝陶瓷与无氧铜的钎焊

电真空应用中,要求高纯氧化铝与无氧铜的连接接头具有较高的强度和气密性.采用Ag-Cu-Ti活性钎料直接钎焊高纯氧化铝陶瓷与无氧铜,研究了钎焊温度和保温时间对接头组成、界面反应以及接头抗剪强度的影响,研究了铜基体材料对钎焊接头组织和界面反应的影响.钎焊温度850～900℃,保温时间20～60 min时,接头抗剪强度接近或达到90 MPa.钎焊工艺参数偏离上述范围时,接头抗剪强度较低.接头由Cu/Ag(Cu),Cu(Ag,Ti)/Cu3Ti3O(TiO2)/Al2O3组成,反应层以Cu3Ti3O为主,个别工艺条件下有一定量的TiO2生成,铜基体视工艺条件的不同对钎焊接头组织有一定影响.     

Al_2O_3陶瓷与TiAl合金真空钎焊接头界面组织及性能

采用AgCuTi活性钎料实现了Al_2O_3陶瓷与TiAl合金的钎焊连接,研究了钎焊接头的界面结构及其形成机制,并且分析了不同钎焊参数对接头界面组织和接头力学性能的影响规律。结果表明:Al_2O_3陶瓷与TiAl合金钎焊接头的典型界面组织为:Al_2O_3/Ti_3(Cu,Al)_3O/Ag(s.s)+Cu(s.s)+AlCu_2Ti/AlCu_2Ti+AlCuTi/TiAl。钎焊过程中,TiAl基体向液态钎料中的溶解量决定了钎焊接头界面组织的形成及其演化。随着钎焊温度的升高和保温时间的延长,Al_2O_3陶瓷侧的Ti_3(Cu,Al)_3O反应层增厚,钎缝中弥散分布的团块状AlCu_2Ti化合物逐渐聚集长大。陶瓷侧界面反应层的厚度和钎缝中AlCu_2Ti化合物的形态及分布共同决定着接头的抗剪强度。当钎焊温度为880℃,保温10 min时,接头的抗剪强度最大,达到94 MPa,此时接头的断裂形式呈现沿Al_2O_3陶瓷基体和界面反应层的复合断裂模式。     

高纯氧化铝与金属钛的钎焊

电真空应用中,要求高纯氧化铝与金属钛的连接接头不仅要有较好的强度,还要有高的气密性.用Ag-Cu-Ti钎料钎焊高纯氧化铝陶瓷与金属钛,钎焊温度为825～875℃,保温时间为15～20min,陶瓷表面为烧结自然表面时,钎焊接头抗剪强度可达到100MPa以上,连接温度过低或过高,保温时间过短或过长均对接头强度不利.陶瓷表面研磨后,接头强度降低.钎料厚度在60μm或105μm对接头强度的影响不大.接头由Al2O3/反应层(Cu,Al,Ti,0)/Ag Cu-Ti化合物/α-Ti(Cu)/Ti构成.反应层主要以Cu3Ti3O和Cu4Ti为主.     

真空热处理对Al2O3陶瓷化学镀Ni-P膜及金属钎焊接头的影响

采用化学镀Ni-P膜法金属化Al2O3陶瓷,并用63Sn-34Pb-2Ag-1Bi钎料膏实现了95%Al2O3陶瓷与45钢之间的低温钎焊.为提高镀膜结合强度并最终提高钎焊接头强度,钎焊前对镀膜陶瓷进行真空热处理.研究了钎焊前真空热处理对Ni-P膜显微组织、钎焊接头显微结构及其强度的影响.结果表明,150～650 ℃高真空热处理会改变Ni-P膜的显微组织,且适当热处理可显著提高钎焊接头强度,在350℃保温1 h可使接头剪切强度到达最高值38 MPa.接头显微结构一般为Al2O3陶瓷/Ni-P镀层/扩散层Ⅰ/富Sn层/钎缝金属层/扩散层Ⅱ/45钢.剪切断裂主要发生在Al2O3陶瓷/Ni-P镀层界面附近,少量扩展到钎缝金属中.     

采用AgCuTi活性钎料真空钎焊MgAl_2O_4透明陶瓷

采用Ag Cu Ti活性钎料箔带分别在880℃/10 min和880℃/60 min两种工艺下对Mg Al2O4陶瓷进行了真空钎焊连接,接头冶金质量良好,两种工艺下接头抗剪强度分别为52.4 MPa和61.3 MPa.微观分析结果表明,靠近陶瓷母材附近生成了连续的扩散反应层结构,结合XRD结果,该层主要由Cu Al2O4和Ti O两种化合物组成;钎缝基体区由Cu(s,s),Ag(s,s)和Ti O相组成.     

Al_2O_3陶瓷与5005铝合金的高频感应钎焊

为实现Al2O3陶瓷与5005铝合金的低温连接,采用Ag-Cu-Ti粉末对Al2O3陶瓷表面进行活性金属化处理.结果表明,当活性金属化温度为880~900℃,保温时间10 min时,在Al2O3陶瓷界面形成连续致密无缺陷的Ti3Cu3O反应层.采用Al-Si钎料对活性金属化Al2O3陶瓷与5005铝合金进行高频感应钎焊,研究了接头的典型界面组织及其形成过程.结果表明,当温度为600℃,保温时间为1 min时,铝合金侧由团状α-Al和晶间渗入的AlAg-Cu共晶组织构成,团状α-Al上有板条状初晶硅出现,Al2O3陶瓷侧有弥散分布的过共晶Al-Si组织,Ti3Cu3O反应层的形成是实现Al2O3陶瓷与5005铝合金可靠连接的关键,接头的最大抗剪强度达到52 MPa.     

AgCu钎料钎焊TC4钛合金与QCr0.8铬青铜接头界面结构及性能

采用AgCu28钎料实现了TC4钛合金与QCr0.8铬青铜的真空钎焊,利用SEM, EDS以及XRD等分析方法确定TC4/AgCu/QCr0.8接头的典型界面结构为TC4钛合金/CuTi +Cu3Ti2 +CuTi2/Ag(s,s) +Cu4Ti/Ag(s,s)+Cu(s,s)/QCr0.8铬青铜. 研究了工艺参数对接头组织和性能的影响. 结果表明,随着钎焊温度和保温时间的增加,钎缝中银铜共晶组织减少,钛铜化合物增多. 接头抗剪强度随钎焊温度的升高先增加后降低,在钎焊工艺参数为890 ℃/0 min时,获得最大抗剪强度449 MPa.保温时间的延长使得接头脆性钛铜化合物增多,接头性能下降,因此随保温时间延长接头抗剪强度显著降低.     

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。