TiAl合金与置氢0.5% TC4钛合金的扩散焊接工艺

对TiAl合金直接扩散焊接和使用置氢0.5%(质量分数) TC4钛合金与TiAl合金的扩散焊接开展了研究,使用了SEM,EDS,XRD和抗剪强度试验等方法分析了焊接接头的组织和性能,研究了焊接温度、连接时间和焊接压力对接头界面及力学性能的影响。结果表明,当工艺参数为1 473 K/60 min/30 MPa时,TiAl合金直接扩散焊接界面孔洞完全消失,接头抗剪强度达到285 MPa;采用置氢0.5% TC4钛合金作为中间层扩散焊接TiAl合金时,当工艺参数为1 123 K/30 min/15 MPa时,扩散焊接界面的孔洞消失,并有一定厚度的反应层生成,接头抗剪强度可达290 MPa,断口界面相组成主要为TiAl,Ti3Al,TiAl2和Ti3Al5等脆性相;相对于TiAl合金直接扩散焊接,采用置氢0.5% TC4合金为中间层扩散焊接TiAl合金能大幅降低TiAl合金扩散焊接工艺参数。     

连接参数对Bi系(BSCCO)超导带材扩散连接接头性能的影响

采用高温直接加压退火工艺扩散连接61芯Bi系高温超导带材。研究了835℃连接温度下接头搭接长度、搭接区窗口的台阶数、保温时间对接头结合界面特征及其超导电性的影响。结果表明,连接参数对接头超导电性Ic影响明显,超导电性低的接头其超导芯结合界面处有未焊合迹象,母材经过835℃扩散连接热循环后超导电性显著降低。     

置氢TC4钛合金与TiAl合金的扩散连接研究

分别对Ti Al合金与TC4钛合金、置氢0.5 wt%的TC4钛合金进行了扩散焊接试验。利用扫描电子显微镜、X射线衍射分析仪、能谱分析仪对接头界面进行了分析,并开展了抗剪强度试验。结果表明,在焊接温度为850℃,连接压力为15 MPa的工艺参数下,当保温时间为5 min时,连接界面存在细小孔洞;当保温时间为15 min时,置氢TC4钛合金的界面孔洞消失,并且产生一定厚度的反应层:保温时间达到30 min时,置氢TC4钛合金与Ti Al合金接头的连接强度平均可达290 MPa。断口分析表明,界面组织主要由Ti Al、Ti_3Al、Ti Al_2和Ti_3Al_5相组成。在相同的扩散焊接工艺规范下,置氢TC4钛合金与Ti Al合金的扩散接头连接强度明显高于未置氢TC4钛合金与Ti Al合金的扩散接头连接强度。     

塑性变形连接工艺对TC17合金/TC4合金连接界面组织与力学性能的影响EI北大核心CSCD

采用塑性变形连接方法制备了TC17合金/TC4合金连接接头,通过金相显微镜(OM)和扫描电子显微镜(SEM)等微观组织表征方法及单向剪切试验,研究了不同连接参数下TC17合金/TC4合金连接界面的微观组织与力学性能,分析了其内在联系,并探究了空洞组织的演化机制。结果表明:连接压力和连接温度对TC17合金/TC4合金连接界面的空洞演化、界面结合率和剪切强度影响更为显著。由于TC17合金/TC4合金连接界面塑性流动和原子扩散的协同作用,连接界面接触面积增大,界面处产生较大的局部应变,空洞由短棒状转变为椭圆形再变为圆形,并逐渐减小直至消失,从而使界面结合率提高,剪切强度增大。     

瞬间液相(TLP)扩散连接GH4169/TC4接头的微观结构及力学性能

为制备镍基高温合金/钛合金复合构件,拓展二者应用领域,以Ti/Ni复合箔片作为中间层,采用瞬间液相(TLP)扩散连接技术制备了GH4169高温合金/TC4钛合金接头,并对接头微观结构、力学性能和连接机理进行了研究和探讨。通过扫描电镜(SEM)、X射线衍射仪(XRD)、能谱分析仪(EDS)、万能试验机和显微硬度仪等对GH4169/TC4接头进行连接界面和断口形貌观察、成分表征、剪切性能和显微硬度测试,结果表明:在连接温度960℃,连接压力5 MPa,保温时间30min的工艺条件下,通过中间层与母材之间的元素扩散和化学反应,形成了"GH4169/Ni(s,s)/TiNi_3/Ti_2Ni/Ti/T_i2Ni/Ni/TiNi+Ti_2Ni/TC4"的多层梯度结构接头,除了"Ni/TiNi+Ti_2Ni"界面处存在一定的孔洞和微裂纹,其余各连接界面连续致密,无明显缺陷。所制备GH4169/TC4接头各区域硬度起伏较大,其中,残余Ti层、Ni层区域硬度最低,有利于缓解接头的内应力;GH4169侧界面区域硬度最高,主要是由于连接过程中形成的Ni(s,s)和TiNi_3硬度较高。结合接头剪切性能测试、断口形貌和物相分析,所制备GH4169/TC4接头抗剪切强度达124.6MPa,开裂发生在TC4附近的"Ni/TiNi+Ti_2Ni"界面区域,呈脆性断裂特征。     

钛合金与不锈钢超塑性扩散连接工艺及机理研究

基于微细晶超塑性扩散连接方法,对TC4钛合金与1Cr18Ni9Ti不锈钢成功实现了直接扩散连接,系统分析了接头性能、界面微观结构及超塑性扩散连接机理。结果发现：TC4钛合金与1Cr18Ni9Ti奥氏体不锈钢直接超塑性扩散连接时,较佳连接工艺规范为：温度T=760~820 ℃,压力p=6~9 MPa,时间t=20~40 min;接头剪切强度τ＝125.3~148.7 MPa。与一般直接扩散连接相比,连接温度降低了约100 ℃,接头的剪切强度提高了1倍以上,且连接试样无明显变形。细化热处理TC4钛合金与1Cr18Ni9Ti不锈钢超塑性扩散连接时,其接头的形成过程大致可分为3个阶段：形成紧密接触阶段、接触表面激活阶段及靠近活化中心的界面冶金结合区形成阶段。     

Cf/SiC复合材料与钛合金(Ti-Zr-Cu-Ni)+W复合-扩散连接

采用(Ti-Zr-Cu-Ni)+W复合钎料作为连接层,在连接温度930℃,保温时间5min的工艺参数下真空钎焊Cf/SiC复合材料与钛合金.利用SEM,EDS和XRD分析接头微观组织结构,利用剪切试验测试接头力学性能.结果表明,钎焊时复合钎料中的钛、锆与C/SiC复合材料反应,在Cf/SiC复合材料与连接层界面生成Ti3SiC2,Ti5Si3和少量TiC(ZrC)化合物的混合反应层,连接层的铜、镍与钛合金中的钛发生相互扩散,在连接层与钛合金界面形成Ti-Cu化合物过渡层.对钎焊接头进行900℃,保温60 min扩散处理后,连接层组织达到均一化,母材TC4合金侧过渡层增厚.扩散处理后接头强度为99 MPa,较钎焊接头强度65 MPa提高了52％.     

TC4/Ni/ZQSn10-2-3扩散连接

采用镍箔做中间层,在真空下对TC4和ZQSn10-2-3进行扩散连接.使用扫描电镜对接头的界面组织进行了研究.确定TC4/Ni/ZQSn10-2-3接头的界面结构是TC4/β-Ti/Ti2Ni/TiNi/TiNi31Ni/Cu(Cu,Ni)/ZQSn10-2-3.通过最优工艺试验,确定最佳工艺参数为连接温度830℃,连接压力10 MPa,连接时间30 min.此时接头最大抗剪强度为135 MPa,接头断口为带有一定塑性的结晶状形貌.通过x射线衍射对断口分析认为,断裂位于TC4/Ni界面处的金属间化合物TiNi3层.     

金刚石/铜复合材料的SPS扩散连接界面组织及力学性能

对金刚石/铜复合材料进行SPS扩散连接试验,并对其连接接头进行了界面扩散分析和剪切性能测试,研究了SPS扩散连接工艺参数对连接界面组织和力学性能的影响。结果表明,随着连接温度升高和保温时间增加,金刚石/铜连接接头扩散界面区域的孔洞和空隙等缺陷减少,元素扩散充分,W逐渐向Cu方向扩散,与母材相比,连接界面W2C相和W相减少。随着扩散连接品质提升,热导率随之增加,焊接接头的最大剪切力和剪切强度增大,剪切断面形貌逐渐产生大量解理面和断裂台阶,并伴有少量撕裂棱,断裂机制由脆性过渡到半解理韧性断裂。扩散温度为750℃,保温时间为90 min时,连接界面整体扩散结合品质较高,剪切强度达到48.83 MPa,热导率为347.73 W/（m·K）。     

CMSX-4单晶高温合金TLP接头组织与性能

采用含Si的BNi-5非晶箔片作为中间层合金对CMSX-4镍基单晶合金棒在放电等离子体烧结炉中进行TLP连接,采用SEM观测了TLP接头在不组织形貌特征,借助于EDS分析了TLP接头界面处的物相组成及其对接头力学性能的影响。采用常温和高温拉伸试验验证了不同焊接工艺条件对TLP接头性能的影响。结果表明,在1 200 ℃/5 kN/20 min工艺参数下可得到满意的TLP接头,此时组织分布较为均匀,常温抗拉强度达到了母材的95%,760 ℃高温抗拉强度达到母材的99%。     

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。