Effect of brazing temperature on microstructure and tensile strength ofγ-TiAl joint vacuum brazed with micro-nano Ti−Cu−Ni−Nb−Al−Hf filler

A novel micro-nano Ti−10Cu−10Ni−8Al−8Nb−4Zr−1.5Hf filler was used to vacuum braze Ti−47Al−2Nb−2Cr−0.15B alloy at 1160−1220℃ for 30 min.The interfacial microstructure and formation mechanism of TiAl joints and the relationships among brazing temperature,interfacial microstructure and joint strength were emphatically investigated.Results show that the TiAl joints brazed at 1160 and 1180℃ possess three interfacial layers and mainly consist of α_(2)-Ti_(3)Al,τ_(3)-Al_(3)NiTi_(2) and Ti_(2)Ni,but the brazing seams are no longer layered and Ti_(2)Ni is completely replaced by the uniformly distributed τ_(3)-Al_(3)NiTi_(2) at 1200 and 1220℃ due to the destruction of α_(2)-Ti_(3)Al barrier layer.This transformation at 1200℃ obviously improves the tensile strength of the joint and obtains a maximum of 343 MPa.Notably,the outward diffusion of Al atoms from the dissolution of TiAl substrate dominates the microstructure evolution and tensile strength of the TiAl joint at different brazing temperatures.

Al2_3/Al2O3 Joint Brazed with Al2O3-particulate-contained Composite Ag-Cu-Ti Filler Material

Microstructure and interracial reactions of Al2O3 joints brazed with Al2O3-particulate-contained composite Ag-Cu-Ti filler material were researched by scanning electron microscopy （SEM）, electron probe microscopy analysis （EPMA）, energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD）. The interracial reaction layer thickness of joints brazed with conventional active filler metal and active composite filler materials with different volume fraction of Al2O3 particulate was also studied. The experimental results indicated although there were Al2O3 particulates added into active filler metals, the time dependence of interracial layer growth of joints brazed with active composite filler material is t^1/2 as described by Fickian law as the joints brazed with conventional active filler metal.

EFFECT OF BRAZING TIME ON TiC CERMET/IRON JOINT BRAZED WITH Ag-Cu-Zn FILLER METAL

The brazing of TiC cermet to iron was carried out at 1223K for 5-20min using Ag-Cu-Zn filler metal. The formation phase and interface structure of the joints were investigated by electron probe microanalysis (EPMA), scanning electron microscopy (SEM) and X-ray diffraction (XRD), and the joint strength was tested by shearing method. The results showed: there occurred three new formation phases, Cu(s.s), FeNi and Ag(s.s) in TiC cermet/iron joint. The interface structure was expressed as TiC cermet/Cu(s.s)+FeNi/Ag(s.s)+a little Cu(s.s)+a little FeNi/Cu(s.s)+FeNi/iron, With brazing time increasing, there appeared highest shear strength of the joints, the value of which was up to 252.2MPa when brazing time was 10min.

Vacuum brazing of TiAl to 42CrMo steel with Ag-Cu-Ti filler metal

Vacuum brazing of TiAl to 42CrMo steel was carried out at 8601000℃ for 5min using Ag-33Cu- 4.5Ti （mass fraction, %） filler metal. Formation phases and microstructures of the joints were investigated by SEM and EPMA. The strength of the joints were evaluated by means of tensile tests. The results show that five interfacial formation phases occur in the brazing seam: AlCuTi and AlCu2Ti compounds, Ag solid solution, Ag-Cu eutectic phase and the reaction layer of TiC adjacent to the steel. The tensile strength of the brazed joints changes with the chang of brazing temperature. When the brazing temperature is 900℃, the tensile strength of the joint is 347MPa. TiAl turbine and 42CrMo steel shaft was brazed and the strength of TiAl/42CrMo turbine rotor was evaluated by means of tensile test, when the tensile load reached 100kN the joint of the rotor kept well.

Research on the influence mechanism of brazing seam geometry on gas pores in brazed joints

Gas pore is a common defect in brazed joint. It lowers the brazing rate and affects the properties of joint. Experimental results show that the application of unequal-gap brazing seam effectively decreases the amount and volume of gas pores, and increases brazing rate.This paper establishes a force model of unequal-gap brazing seam, and proposes the constitutive relationship between expulsion force and curvature. The force condition of gas bubble in geometrically different brazing seams were calculated, and the results were verified with experiments. The results show that the expulsion force of gas bubble is positively correlated to the curvature of the seam geometry. The gas bubble tends to move towards the direction with large curvature and wider gap. The directional bubble movement is obtained through varying the configuration of gas-liquid interface to meet geometric conditions. Gas bubble accelerates to expulse with arc, hyperbola and cycloid brazing seams, in which the best drainage effects of gas bubble occur for cycloid seams.

Microstructure and properties of the joints of Cu/Cu and metallized Cu / kovar brazed with a low-silver vacuum brazing filler metal

In an attempt to develop low-silver brazing filler metals used for hermetic sealing materials in the vacuum interrupter industry,the ternary Ag-50Cu-5Ga low-silver vacuum brazing filler metal was investigated.The melting temperature was measured by differential scanning calorimetry(DSC),and the brazability of Ag-50Cu-5Ga alloy on copper and metallized copper/kovar were ascertained at 850℃under 1×10-4 Pa in this article.The microstructures of the filler metal and the joints have been analyzed by using scanning electron microscopy(SEM),equipped with an energy dispersive spectroscopy.The results show that vacuum brazing was success to join with copper or metallized copper/kovar using Ag-50Cu-5Ga filler and reliable joints were obtained.There were Ag-rich phase,Cu-rich phase and a fine eutectic structure of Ag-based solid solution and Cu-based solid solution in the copper joints and the width of brazing seam is about 60μm.The joints of kovar alloy to copper after surface nickel plating was composed of AgCu eutectic phase,Ag,Cu,Cu2Ga and CuNi2 phase.The tensile strength was 167 MPa and 150 MPa,respectively.The tensile results of joints show that the joint strengths were equivalent to the traditional brazing filler metals.

2D Finite Element Computer Analysis of Strength for Brazed Joint of Cemented Carbide and Silver Brazing Filler Metal

Brazing has a wide acceptance in industries and its simplicity in variety of application attracts more and more patronage. The strength of brazing joint determines the reliability of brazed engineering components. So the need to ascertain the reliability or to predict its failure （without some destructive testing） becomes high even with a computer aided analysis using the Finite Element Analysis. Here, we have employed the services of FEA software, Abaqus CAE, as a tool for the computer calculation to investigate a joint case of cemented carbide brazed with silver-based filler metal. In this paper, 2D analysis has been adopted because the thickness of the material （in 2D） does not influence the final calculation results. We have applied constant loading and constant boundary condition to explore data from the elastic and plastic strain analysis through which we were able to predict the maximum joint strength with respect to the joint thickness. The pattern of the meshing was also significant. And the result could be transferable to a real-life field situation. The final results showed that there is an optimum thickness of the filler metal with the maximum strength which matches that obtained from experiment.

Brazeability evaluation of Ti-Zr-Cu-Ni-Co-Mo filler for vacuum brazing TiAl-based alloy

Ti-47Al-2Nb-2Cr-0.15B(mole fraction,%)alloy was vacuum brazed with amorphous and crystalline Ti.25Zr-12.5Cu-12.5Ni-3.0Co-2.0Mo(mass fraction,%)filler alloys,and the melting,spreading and gap filling behaviors of the amorphous and crystalline filler alloys as well as the joints brazed with them were investigated in details.Results showed that the amorphous filler alloy possessed narrower melting temperature interval,lower liquidus temperature and melting active energy compared with the crystalline filler alloy,and it also exhibited better brazeability on the surface of the Ti.47Al.2Nb.2Cr.0.15B alloy.The TiAl joints brazed with crystalline and amorphous filler alloys were composed of two interfacial reaction layers and a central brazed layer.Under the same conditions,the tensile strength of the joint brazed with the amorphous filler alloy was always higher than that with the crystalline filler alloy.The maxmium tensile strength of the joint brazed at 1273 K with the amorphous filler alloy reached 254 MPa.

银包覆法制备Ag-Cu-TiH_(2)焊膏的研究

Ag-Cu-Ti钎料可以实现Cu和Si_(3)N_(4)陶瓷的连接。然而,钎焊过程中Ti倾向于和Cu反应形成金属间化合物,降低了界面结合强度。本文采用化学还原法,以抗坏血酸为还原剂、Na_(2)EDTA为分散剂,30℃保温30 min,在Cu和Ti H_(2)表面包覆了一层均匀致密的Ag层。由于高活性的Ti降低了熔融Ag的表面张力,使得润湿角降低,焊料的铺展性能更好,此外,包覆Ag后显著抑制了焊膏中Ti和Cu的反应,提高了焊膏的活性,从而提高了覆铜板的界面结合强度。研究发现,包覆银的钎料在陶瓷上的铺展面积提高了8.4%;制备的陶瓷覆铜板剥离强度提高了16.7%。

Ag-Cu-Ti钎料中Ti元素在金刚石界面的特征

研究了金刚石钎焊接头中碳化物形成元素Ti与金刚石 (或石墨 )之间的相互作用行为。通过对接头界面处的成分分布和断口形貌观察 ,分析了Ti的作用机理、新生化合物TiC的断口形式及生长规律。结果表明 :在一定的条件下 ,Ti元素与组成金刚石 (或石墨 )的碳元素发生反应形成TiC层 ;碳化物层使钎料与金刚石之间产生冶金结合 ;TiC与金刚石之间存在有明显的界面 ,TiC断口的微观表面形态呈韧窝状 ;在金刚石表面初始形成的TiC的生长方向与金刚石的晶向指数有关。

Ag-Cu-Ti钎料在金刚石表面的润湿状况

针对金刚石的钎焊问题，利用扫描电镜和电子探针分析、Ｘ射线能谱分析、Ｘ射线结构分析等方法，对Ａｇ－Ｃｕ－Ｔｉ钎料在金刚石表面的润湿状况进行了试验研究．结果表明，含Ｔｉ量对钎料的润湿状况有一定影响、界面间Ｃ，Ｔｉ元素的扩散及ＴｉＣ的形成有助于改善钎料的润湿状况．

Ag-Cu-Ti活性钎料真空钎焊钼和石墨结合质量研究

为了实现石墨与钼的高强连接,实验采用活性钎料Ag-Cu-Ti作为填充材料,研究了钎焊过程中采用的工艺及不同种类石墨对真空钎焊接头组织结构和性能的影响,进一步探讨了界面结合机理。利用光学显微镜分析了接头微观形貌,采用能谱仪确定了接头的成分分布,采用自行设计的模具测试了接头的剪切强度。结果表明,Ag-Cu-Ti钎料与两侧钼和石墨基体均形成了良好的结合界面,接头抗剪强度达到了石墨基材强度的80%以上;石墨密度对接头性能的影响比较大,导致钎缝区出现不同的界面形貌,可以通过表面物理改性的方法改善接头质量。

采用Ag-Cu-Ti钎料钎焊C_f/SiC接头的组织和强度

选用Ag-35.5Cu-1.8Ti和Ag-27.4Cu-4.4Ti两种钎料,在880℃/10min钎焊规范下进行了Cf/SiC陶瓷基复合材料的钎焊实验。实验结果表明,钎焊接头中央为典型的Ag-Cu共晶组织,而在钎料与Cf/SiC母材的界面处形成了扩散反应层,Ti在该层中富集。通过界面X射线衍射分析,确定界面存在TiC相,但未检测到Ti-Si相。分析了界面反应机理。接头强度试验结果表明,采用Ag-35.5Cu-1.8Ti钎料获得接头的三点弯曲强度为132.5MPa,而Ag-27.4Cu-4.4Ti对应的接头强度为159.5MPa,分析认为,Ti在钎料中的活性是决定接头性能的关键因素之一,即接头强度随着钎料中Ti活性的提高而呈现增加的趋势。

金刚石/铜复合材料与氧化铝陶瓷的Ag-Cu-Ti活性钎焊(英文)

金刚石/铜复合材料具有低膨胀系数和高热导率等优异性能,使其成为一种理想的电子封装材料。采用97%(72Ag-28Cu)-3%Ti活性钎料对金刚石/铜复合材料和氧化铝陶瓷进行钎焊。发现活性钎料在氧化铝陶瓷和金刚石薄膜表面均具有良好的润湿性,在两者表面的平衡润湿角均小于5°。讨论了主要钎焊条件(如钎焊温度和保温时间等)对接头性能的影响。发现钎焊过程中Ti元素聚集在金刚石颗粒的表面形成TiC化合物,且TiC化合物的形貌与钎焊接头的剪切强度具有紧密联系。推测合适的TiC化合物层厚度可改善钎焊接头的剪切强度,而颗粒状的TiC化合物及过厚的TiC化合物层却会损害钎焊接头的性能。获得的最大剪切强度为117MPa。

Ag-Cu-Ti合金制备技术及钎焊应用综述

介绍了Ag-Cu-Ti活性钎料的主要制备方法,常用的Ag-Cu-Ti活性钎料及熔化温度,Ag-Cu-Ti钎料钎焊各种陶瓷与陶瓷或陶瓷与金属,Ag-Cu-Ti活性钎料钎焊金刚石、石墨、玻璃、立方氮化硼、复合材料的应用研究进展及Ag-Cu-Ti活性钎料的改性研究。

采用Ag-Cu-Ti+Mo复合钎料钎焊Si_3N_4陶瓷

采用Ag-Cu-Ti+Mo复合钎料连接Si3N4陶瓷,利用SEM,TEM,Nanoindentation研究了钎料内钼颗粒含量对接头组织和力学性能的影响.结果表明,在Si3N4/钎料界面处形成了一层致密的反应层,该反应层由TiN和Ti5Si3组成.接头的中间部分由银基固溶体、铜基固溶体、钼颗粒和Ti-Cu金属间化合物组成.借助于纳米压痕技术测定了接头内Ti-Cu化合物以及钎料金属的弹性模量和硬度值.随着钎料内钼颗粒含量的提高,母材/钎料界面反应层厚度逐渐降低;钎料金属中Ti-Cu化合物数量增多;此外,银和铜基固溶体组织逐渐变得细小.当添加5%Mo时,得到最高的接头强度429.4 MPa,该强度相比合金钎料提高了114.7%.

PERFORMANCE OF BRAZED DIAMOND CUP-TYPE WHEELS WITH DEFINED GRAIN PATTERN IN GRINDING CEMENTED CARBIDE

A new cup-type grinding wheel of the brazed monolayer diamond is developed with a defined grain pattern on the wheel surface. Grinding performance of the brazed wheel in the surface grinding of cemented carbide is studied. Experimental results show that when continuous dry grinding is employed, grits of the brazed diamond grinding wheel fail mainly in attritious wear and fracture modes and no pull-out ones are found in conventional electroplated and sintered diamond wheels. It indicates the strong retention of brazing alloy to diamond grits and the longer service life of the wheel. In addition, the ground surface has good roughness. The theoretical surface roughness agrees well with experimental results.

Ag-Cu-Ti活性钎料热力学分析

在陶瓷与金属的活性钎焊连接技术中 ,Ag -Cu -Ti合金是研究和应用最多的钎料之一。合金组元Ti的活度是影响钎料 /陶瓷界面反应的关键因素 ,对钎料与陶瓷的润湿性和连接能力起着重要的作用。作者借助热力学对Ag -Cu -Ti活性钎料进行了热力学分析 ,重点分析了Ti的热力学活度及其与组分浓度之间的关系 ,计算了各组分之间的相互作用参数。分析和计算结果表明 ,Ti的活度随着Cu含量的增加而减小 ,随着Ag含量的增加而增大 ;Ag与Ti之间存在较大的排斥作用 ,两者的相互作用参数为 32 .83kJ/mol;而Cu与Ti之间存在强烈的吸引作用 ,其相互作用参数为 - 16 .14kJ/mol;Ag -Cu -Ti合金中添加某些与Cu的结合力大、与Ti的结合力小、且与合金组元不形成高熔点化合物或脆性相的合金元素 。

Ag-Cu-Ti钎焊金刚石/铜复合材料的组织和性能

采用97(72Ag-28Cu)-3Ti活性钎料钎焊了Diamond/Cu复合材料和Al2O3陶瓷,研究了主要钎焊条件如钎焊温度和保温时间对接头强度的影响。结果表明,钎焊过程中Ti元素易聚集在金刚石颗粒周围并形成TiC化合物层。TiC化合物的形貌与Diamond/Cu钎焊接头剪切强度有密切关系,金刚石表面生长适当厚度的TiC化合物层能增强钎焊接头的剪切强度,但如果TiC为颗粒状或TiC化合物层生长过厚,将削弱钎焊接头的剪切强度。钎焊接头的最大剪切强度可达117 MPa。

Microstructure and shear strength of reactive brazing joints of TiAl/Ni-based alloy

Reactive brazing of TiAl-based intermetallics and Ni-based alloy with Ti foil as interlayer was investigated. The interfacial microstructure and shear strength of the joints were studied. According to the experimental observations, the molten interlayer reacts vigorously with base metals, forming several continuous reaction layers. The typical interfacial microstructure of the joint can be expressed as GH99/（Ni,Cr）ss（γ）/TiNi（β2）＋TiNi2Al（τ4）＋Ti2Ni（δ）/δ＋Ti3Al（α2）＋Al3NiTi2（τ3）/α2＋τ3/TiAl. The maximum shear strength is 258 MPa for the specimen brazed at 1000°C for 10 min. Higher brazing temperature or longer brazing time causes coarsening of the phases in the brazing seam and formation of brittle intermetallic layer, which greatly depresses the shear strength of the joints.