瞬间液相扩散连接模型及发展现状

瞬间液相扩散连接（TLP-DB）方法以其独有的性能优势，在先进材料连接领域得到广泛的重视和应用。综述了瞬间液相扩散焊中接触熔化、液相均匀化、等温凝固以及固相成分均匀化阶段的理论模型及发展状况．并对现有模型进行了分析和讨论。     

碳钢/不锈钢的瞬间液相扩散复合

用扫描电镜、能谱分析等方法,研究了H62黄铜为中间层的20钢/304不锈钢瞬间液相扩散复合后结合区的组织、成分与性能。结果表明:在950～1100℃扩散退火0.5～1h,20钢与304不锈钢可以获得良好的冶金结合;当温度较高,时间较长时,在界面附近的20钢一侧,因合金元素含量提高,淬透性提高,导致空冷形成高硬度的马氏体组织;Fe、Cr、Ni向H62黄铜中扩散富集,形成高硬度的岛状组织。     

瞬时液相扩散焊连接压力的研究

瞬时液相扩散连接过程中由于过渡液相的产生降低了连接过程中所需要的压力,但是压力在瞬时液相扩散连接过程中起着重要的作用,是保证焊接接头质量,提高焊接效率的主要影响因素之一。本文对连接压力在连接过程中排除氧化膜、减少等温凝固时间等作用进行了总结,并对其选择依据和控制原则进行了讨论。     

TiNi形状记忆合金与不锈钢的瞬时液相扩散焊

采用AgCu金属箔作中间过渡层,对TiNi形状记忆合金与不锈钢进行了瞬时液相扩散焊,分析了接头的显微组织、元素分布和物相组成等,研究了接头的抗剪强度和断裂方式。结果表明:接头界面区由TiNi侧过渡区,中间区,不锈钢侧过渡区组成,主要相分别为Ti(Cu,Ni,Fe),AgCu,TiFe等。连接温度为860℃,保温时间为60min,连接压力为0.05MPa时,接头最大抗剪强度为239MPa。断裂发生在TiNi母材和AgCu中间层扩散界面上,断口为混合断裂形貌。通过中间层等温凝固过程动力学模型,结合界面形貌和元素扩散分析,认为TiNiSMA与不锈钢异种材料瞬时液相扩散焊过程存在明显的非对称性。     

珠光体耐热钢12Cr1MoV的瞬时液相扩散连接工艺

研究了珠光体耐热钢12Cr1MoV的瞬时液相扩散连接工艺,分析了接头的力学性能和显微组织,结果表明:采用非晶合金FeNiCrSiB为中间层.连接温度为1200℃,连接压力为4MPa,保温时间在2、3、4min时均可得到良好的焊接接头,并随着保温时间的延长,元素扩散更加充分,接头的力学性能和组织性能都得到了提高.     

高效焊管新工艺——金属管液相扩散焊

采用镍基非晶态箔带作中间层,在加压情况下(约几MPa)使之熔化、保温,进行了钢管瞬间液相 (TLP)扩散焊试验。结果表明,可以获得无夹杂的致密界面;接头过渡区的最终厚度显著变薄;焊后中间层主组元由焊前的Ni变为Fe;容易获得性能合格接头。值得指出的是,焊接时间约为3min,远低于手弧焊所需时间。     

高效焊管新工艺--金属管液相扩散焊

采用镍基非晶态箔带作中间层，在加压情况下（约几MPa）使之熔化、保温，进行了钢管瞬间液相（TLP）扩散焊试验。结果表明，可以获得无夹杂的致密界面；接头过渡区的最终厚度显著变薄：焊后中间层主组元由焊前的Ni变为Fc；容易获得性能合格接头。值得指出的是，焊接时间约为3min，远低于手弧焊所需时间。     

瞬间液相扩散焊与钎焊主要特点之异同

从焊接进程、凝固、氧化物的破碎、中间层与钎料的区别、接头组成、脆性相的形成与消除、压力的作用、接头强化机理等方面总结分析了瞬间液相扩散焊与钎焊的区别。强调指出了下述关键点 :(1)中间层的选取是获得两种不同焊接方法接头的首要前提 ;(2 )在钎焊中侧重点是润湿性 ,它是保证接头获得一定强度的首要前提与主要手段 ;(3 )在瞬间液相扩散焊过程中 ,除了润湿性之外 ,更为关注的是降熔元素的扩散。中间层中降熔元素向母材的持续扩散是TLP接合中液态区增宽、破碎氧化膜、等温凝固、均匀化现象的本质原因 ;降熔元素向母材的充分扩散及由此而出现的中间层成分的合理改变是TLP焊接成败的命脉     

硬质合金/钢活性液相扩散焊接技术研究

为解决冲孔机硬质合金冲头由于焊接强度不够导致使用中冲头容易脱落,进而大大降低冲头的使用寿命的问题,采用Ti/Cu组合中间层的活性瞬间液相扩散焊(A-TLP)进行了"硬质合金/钢"的焊接试验,并在相同条件下与钎焊进行了对比,采用自制夹具与电子拉伸试验机相结合的方式进行了焊接接头剪切强度的检测。实验发现,对于"YG6X硬质合金/45号钢"的焊接来说,活性瞬间液相扩散焊(A-TLP)的焊接强度远高于钎焊,两种焊接接头的剪切强度分别为173.52 MPa和112.12 MPa。     

金属基复合材料过渡液相(TLP)扩散焊中间层设计的改进

为防止复合材料过渡液相（TLP）扩散焊焊缝中心区域出现增强相偏聚，归纳总结了5种中间层设计的改进方法：（1）适当减小中间层厚度；（2）采用合金型中间层；（3）加覆（镀）阻挡层；（4）中间层材质的优化；（5）减少液态金属的挤出量。评述了各种方法的优缺点。     

金属基复合材料过渡液相(TLP)扩散焊中间层设计的改进

为防止复合材料过渡液相(TLP)扩散焊焊缝中心区域出现增强相偏聚,归纳总结了5种中间层设计的改进方法:(1)适当减小中间层厚度;(2)采用合金型中间层;(3)加覆(镀)阻挡层;(4)中间层材质的优化;(5)减少液态金属的挤出量。评述了各种方法的优缺点。     

保温时间对瞬时液相扩散连接的Ti3Al /Ti2AlNb接头微观结构及力学性能的影响

采用Ni-Ti复合箔片作为中间层,在990 ℃、低连接压力（0.1 MPa）下,通过瞬时液相（TLP）扩散连接制备了Ti₃Al/Ti₂AlNb异种合金接头。分析了保温时间（10~90 min）对Ti₃Al/Ti₂AlNb接头微观结构及力学性能的影响,并研究了TLP扩散连接接头的界面演变和形成机制。结果表明,Ti₃Al/Ti₂AlNb接头具有典型的“Ti₃Al | Al_0.5Nb_0.5Ti₃ | 残余 Ni | NiTi | NiTi₂ | 残余 Ti | Al_0.5Nb_0.5Ti₃ | Ti₂AlNb”多层梯度结构。随着保温时间的延长,接头的抗剪切强度先增大后减小,当保温时间达到60 min时,Ti₃Al/Ti₂AlNb接头的抗剪切强度最大,达到167±12 MPa。另外,接头的断裂主要发生在Ti₂AlNb/Ti附近的NiTi₂层,并向Ti层延伸,呈现出脆性断裂的特征。     

钛合金与不锈钢的超塑性扩散连接研究

采用镍箔作为中间过渡层,在真空下对TC4钛合金与1Cr18Ni9Ti不锈钢进行了微细晶超塑性扩散连接。通过扫描电镜、X射线衍射及剪切强度试验等方法,对连接接头进行了微观分析和剪切强度测试。结果表明:采用镍箔作中间过渡层,能有效地防止铁与钛、碳间的相互扩散和迁移,避免界面上更多的金属间化合物产生,从而提高了接头性能。在连接温度为790℃、连接压力为3MPa,连接时间为30min的条件下,可获得钛合金与不锈钢的牢固连接,接头剪切强度可达131.1MPa,且试样无明显变形。     

铝基复合材料瞬间液相扩散连接接头的组织与力学性能

采用扫描电镜、能谱仪及电子拉伸试验机系统地研究了Cu,Ag作为中间层铝基复合材料瞬间液相扩散连接接头的组织与力学性能。根据组织结构特点接头可分为增强相偏聚区、增强相贫化区和母材区。增强相偏聚区的组织主要为Al2O3颗粒和铝合金基体，并含有汪量的MgAl2O4化合物，对于Cu中间层接头还含有少量的Al2Cu化合物。连接温度、连接时间和中间层厚度对接头抗剪强度具有较明显的影响。在一定条件下，Cu,Ag中间层接头的抗剪强度分别为82－99MPa和86－109MPa。增强相偏聚区是接头最薄弱的区域，减少增强相的偏聚是进一步改善接头力学性能的重要途径。     

金属基复合材料钎焊与液相扩散焊焊接区增强体/基体界面演变行为及其对接头强度的影响

综述了金属基复合材料中增强体／基体（R／M）界面接合类型，对比了焊接条件下与制备条件下R／M界面结合特征的差别。据此首次提出将界面分为一次界面与二次界面的分类方法；进而提出了钎焊与液相扩散焊热循环中R／M界面演变行为模式，即一次界面的损伤／解体与二次界面的重建。讨论了R／M界面演变行为及其对接头强度的直接与间接影响。     

Effect of bonding temperatures on the transient liquid phase bonding of a directionally solidified Ni-based superalloy,GTD-111

The bonding phenomenon and the mechanism involved in the transient liquid phase bonding (TLP Bonding) of directionally solidified Ni-based superalloy GTD-111 was investigated. At a bonding temperature of 1403 K, the liquid insert metal was eliminated by isothermal solidification, which was controlled by the diffusion of B and Si into the base metal. The solids in the bonded interlayer simultaneously grew epitaxially from the mating base metal inward from the insert metal. The number of grain boundaries formed at the bonded interlayer corresponded with those of the base metal. Liquefaction at the grain boundary and dendrite boundary occurred at a temperature of 1433 K. At a bonding temperature of 1453 K which is higher than the liquefaction temperature of the grain boundary, liquids of the insert metal were connected with liquated grain boundaries; this connection extended as far as the grain boundary, which was approximately 1.5 mm from the interface. The composition of this liquid was a mixture of the insert metal and phase that existed at the grain boundary. At extended holding times, liquid phases gradually decreased, and liquids with a continuous band shape develop into distinct islands. However, the liquid phases did not disappear after a holding period of 7.2 ks at 1453K. The extended isothermal solidification process at the bonding temperature, which is higher than the liquefaction temperature for the grain boundary, was controlled by the diffusion of Ti. This resulted in its preferential liquefaction compared to B or Si in the insert metal.     

Effect of bonding temperature on transient liquid phase bonding behavior of a Ni-based oxide dispersion-strengthened superalloy

The effect of joining temperature on the transient liquid phase (TLP) bonding of MA758 superalloy was investigated. The TLP bonds were made at temperatures of 1100 and 1200 °C. Analysis was undertaken to determine the changes within the joint microstructure. The bonding temperature affected the extent of parent metal dissolution, the time for isothermal solidification, and the attainment of microstructural continuity across the joint region. Bonding at 1100 °C did not result in extensive parent metal dissolution, and subsequent shear testing showed failure through the center of the joint. However, bonding at 1200 °C increased parent metal dissolution resulting in significant agglomeration of Y₂O₃ particles at the joint interface. Failure was observed along the joint interface in regions depleted of strengthening particles. Bonding at a higher temperature reduced the time for isothermal solidification but also reduced the strain energy of the oxide dispersion-strengthened alloy so that grain growth across the joint region could not be achieved.     

Effect of mechanical properties using different filler metals on wide-clearance activated-diffusion-brazed Ni-based superalloy

The investigation of mechanical properties and failure mechanism of activated-diffusion-brazed (ADB) joints in IN-738 plate were conducted. Joints of this type, which had wide clearance, were formed using the brazing alloys Nicrobraz 150 and DF4B. The microstructural characterization showed that chromium borides with a blocky morphology were present in joints associated with the two brazing alloys. A major difference in matrix phase chemistry was observed, however, for the two brazing alloys, e.g., an Ni-B eutectic phase was observed in Nicrobraz 150, but DF4B exhibited a coarsened gamma prime (γ) phase and an absence of a nickel boride matrix phase. Results of tensile test showed that ADB specimens using DF4B brazing alloy exhibited 95% nominal tensile strength of IN-738 base materials. Fracture cracks in the joint area were initiated and confined to dispersed chromium boride sites. However, tensile test of ADB specimens using Nicrobraz 150 showed poor tensile properties at all testing temperatures, and their fractures were initiated at a brittle nickel boride site and propagated along the weak-bonded interface between the Ni-B eutectic phase and base materials.