V/Nb复合中间层热等静压扩散连接钢/钨接头的组织与性能

采用V/Nb复合中间层成功实现了钢/钨热等静压扩散连接,并对高温低压(1 050 ℃, 20 MPa)和低温高压(950 ℃, 100 MPa)条件下形成的接头界面结构及连接强度进行了探究. 结果表明,高温低压组和低温高压组接头均呈W/Nb/V/钢四层结构,抗剪强度分别为96.9 MPa和104.2 MPa,断裂位置均为无明显化学反应发生在Nb/V界面. 与高温低压组相比,降低连接温度并提高连接压强在一定程度上有助于形成高致密度的连接接头,但不能促进薄弱界面(Nb/V)的元素扩散并显著提高接头的连接强度.     

钴/镍复合中间层真空扩散连接钨与钢

以钴粉/镍箔为复合中间层,采用800,900和1 000 ℃等三种连接温度,加压10 MPa并保温120 min的工艺条件,对钨/钢真空扩散连接. 研究了接头的微观组织、成分分布、力学性能及断口特征. 结果表明,连接温度为800 ℃和900 ℃时,钨/中间层界面金属间化合物生成很少,对应接头抗剪强度分别为186 MPa和172 MPa,断口均位于钨母材中近界面的位置,为典型解理断裂形貌;当连接温度升至1 000 ℃时,钨/中间层界面生成厚度小于2 μm的连续金属间化合物层,接头抗剪强度降至115 MPa,断裂也发生在钨母材中近界面的位置,断口大部分区域为沿晶断裂特征.     

Be/CuCrZr合金扩散连接的界面行为

在不同表面粗糙度的Be侧镀Ti/Cu中间层,采用热等静压技术将铍与CuCrZr合金进行扩散连接。通过AES、SEM(EDS)、室温剪切试验和XRD等分析其镀层形貌及成分、界面特性与相结构。结果表明:9μmTi、35μmCu镀层带征较为均匀,影响扩散连接强度的元素较少,采用双靶单侧镀复合膜的工艺有利于减少Ti镀层的氧化;界面剪切强度明显提高,最高可达243MPa,Be表面粗糙度的不同对强度影响不明显;Be-Ti连接强度高,剪切断裂均发生在Cu镀层。     

钨/钛/MA956钢SPS扩散连接的界面结构和力学性能

在950℃/10MPa的工艺条件下,采用高效的放电等离子烧结技术对钨/钛/MA956进行真空扩散连接。焊后通过显微硬度测试和剪切强度试验评估SPS扩散连接的接头力学性能;并利用扫描电镜、能谱仪以及X射线衍射仪对接头的界面组织和断裂特征进行观察分析。结果表明,该技术成功实现了W/Ti/MA956在10～30min的保温时间下的可靠连接。钨/钛/MA956钢接头界面由W-Ti固溶体层、Ti层以及Ti/MA956金属间化合物(FeTi、Fe2Ti和Cr2Ti)层组成。Ti/MA956界面由于金属间化合物的生成,具有最高的硬度,硬度峰值达580HV。随着保温时间的增加(10、20、30min),接头平均剪切强度由130.2MPa(10min)提高到163.5MPa(20min)再降到125MPa(30min);接头断裂均发生在Ti/MA956界面。     

镀铜/镍烧结钕铁硼永磁体与DP1180钢钎焊接头的组织与性能

采用Zn-6Sn-5Bi钎料对镀Cu/Ni的烧结NdFeB永磁体和DP1180钢进行钎焊连接,对比分析了2种镀层条件下钎焊接头的微观组织和力学性能。结果表明,对于镀Cu的烧结NdFeB永磁体和DP1180钢的钎焊接头,Cu在钎料中扩散并与Zn、Fe反应生成脆性金属间化合物,导致钎缝中出现裂纹和孔洞。与无镀层时的烧结NdFeB永磁体和DP1180钢的钎焊接头相比,接头的剪切强度由61.9 MPa降低至52.3 MPa;对于镀Ni的烧结NdFeB永磁体和DP1180钢的钎焊接头,Ni集中分布在NdFeB一侧的界面处,并且由于Sn和Bi的扩散形成了不同的扩散层,其剪切强度提高至78.1 MPa。     

Al2O3/Kovar热等静压扩散层的组织与性能

采用Ti-Ni及Ag-Cu-Ti为过渡层材料实现了Al₂O₃陶瓷与Kovar合金的热等静压扩散连接。利用金相显微镜、SEM、EDS和万能试验机等测试分析了Al₂O₃/Kovar扩散接头的显微组织、界面反应及剪切强度。结果表明,Al₂O₃/Ti-Ni/Kovar接头连接界面处无孔洞等显微缺陷,但其强度及气密性较低,剪切强度及漏率分别为67 MPa及2×10^-10 Pa·m³/s;Al₂O₃/Ag-Cu-Ti/Kovar接头之间界面连接良好,无明显显微缺陷,接头强度及气密性较高,剪切强度及漏率分别为85 MPa及5×10^-11 Pa·m³/s。     

扩散焊接钨/钒/钢体系的界面结构及力学性能

采用厚度为0.5 mm钒片作为中间层,在1050℃/10 MPa/1 h的工艺条件下,对钨/钢异种材料进行扩散焊接.采用扫描电镜、能谱仪和纳米压痕分别对接头的微观组织、元素分布及显微硬度进行分析和测试;对接头的拉伸性能进行测试,并对其断口形貌和元素分布进行分析.结果表明,利用母材与中间层之间元素的相互扩散,可实现钨/钢材料的焊接;钨/钢焊接接头界面区由钨-钒固溶体层、未反应钒层及钒-钢扩散层3部分组成,其中钒-钢界面层结构为钒/VC层/脱碳层/钢;钢/钒扩散层具有最高的显微硬度;钨/钢接头抗拉强度为75 MPa,含脆性相VC的钒/钢界面是接头失效的主要断裂源.     

TC4钛合金与Al6061铝合金热等静压扩散连接接头的界面特征及力学性能

对TC4钛合金和Al6061铝合金的异种金属进行了热等静压扩散连接实验,研究了TC4/Al6061连接接头的界面特征、形成机制和力学性能,并通过热力学分析解释相关实验现象。结果表明,热等静压扩散连接及后续退火处理后,两侧母材元素发生了明显的互扩散,其中Si、Mg元素在化学势驱动力作用下分别富集于扩散过渡区和Al侧界面。接头界面发生冶金反应生成TiAl₃、TiAl、Ti₃Al等金属间化合物,通过有效生成热模型计算表明TiAl₃相优先生成。硬度实验表明界面生成的Ti-Al金属间化合物具有较高的硬度。拉伸实验显示接头最大抗拉伸强度达到了144 MPa。     

基于SPS烧结的M42/45钢双金属接头及性能

利用放电等离子烧结技术(SPS)研究了M42粉末高速钢/45钢双金属连接技术,分析了连接接头的界面形貌,测试了连接接头的界面结合强度.结果表明:在970℃×10 min×70 MPa烧结工艺下,可一次性实现M42粉末高速钢的烧结及其与45钢的连接;接头的M42粉末冶金高速钢部分,显微组织均匀,碳化物细小、无偏析,经工艺1180℃×5 min×550℃×1 h热处理后,硬度达到67.36 HRC;M42/45钢连接接头组织致密且均匀,界面两侧有元素扩散,属冶金结合,界面结合强度可达到550 MPa.     

铜-不锈钢真空扩散连接工艺及界面微观结构

采用电镀工艺,在纯铜基体表面制备出约2.74μm的单质Au镀层,在950℃,1MPa压力下实现了铜与不锈钢的真空扩散接合,并与铜-钢直接连接接头进行界面显微结构对比.试验结果表明:在直接连接800℃时结合界面钢侧存在明显的元素沿晶界扩散现象,接头抗剪强度158MPa,约为铜母材强度的86%;添加单质Au镀层中间层时,有...     

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).     

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.     

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.     

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。