Influences of diffusion bonding process parameters on bond characteristics of Mg-Cu dissimilar joints

In many circumstances,dissimilar metals have to be bonded together and the resulting joint interfaces must typically sustain mechanical and/or electrical forces without failure,which is not possible by fusion welding processes.The melting points of magnesium(Mg)and copper(Cu)have a significant difference(nearly 400℃)and this may lead to a large difference in the microstructure and joint performance of Mg-Cu joints.However,diffusion bonding can be used to join these alloys without much difficulty.This work analyses the effect of parameters on diffusion layer thickness,hardness and strength of magnesium-copper dissimilar joints.The experiments were conducted using three-factor,five-level,central composite rotatable design matrix.Empirical relationships were developed to predict diffusion layer thickness,hardness and strength using response surface methodology.It is found that bonding temperature has predominant effect on bond characteristics.Joints fabricated at a bonding temperature of 450℃, bonding pressure of 12 MPa and bonding time of 30 min exhibited maximum shear strength and bonding strength of 66 and 81 MPa, respectively.

Vacuum diffusion bonding of Ti_(2)AlNb alloy and TC4 alloy

The Ti_(2)AlNb alloy was joined with TC4 alloy by vacuum diffusion bonding.The relationship between bonding parameters,and joint microstructure and shear strength was investigated.The results indicated that the diffusion of Al,Ti,Nb and V elements across bonding interface led to the formation of three reaction layers:B2/βlayer andα2 layer on the TC4 side,andα2+B2/βlayer on the Ti_(2)AlNb side.The bonding temperature determined the atomic activity,thus controlling the growth of reaction layers and influencing the shear strength of the joint.When the Ti_(2)AlNb alloy and TC4 alloy were bonded at 950℃for 30 min under 10 MPa,the shear strength of the joint reached the maximum of 467 MPa.The analysis on the fracture morphology showed that the fracture occurred within the B2/βlayer and the fracture model was ductile rupture.Meanwhile,the formation mechanism of the Ti_(2)AlNb/TC4 joint was discussed in depth.

Bonding interface characteristic and shear strength of diffusion bonded Ti-17 titanium alloy

The bonding interface characteristic and shear strength of diffusion bonded Ti-17 titanium alloy at different bonding time were investigated. The results show that the average size of voids decreases while the amount of voids decreases after increasing to the maximum value with the increasing bonding time. The irregular void with a scraggly edge tends to an ellipse void with smooth surface and then changes to a tiny void with round shape. The grains across bonding interface occur at bonding time of 60 min. The shear strength of bond increases with increasing bonding time, and the highest shear strength of bond is 887.4 MPa at 60 min. The contribution of plastic deformation on the void closure and the increase of shear strength is significant even though the action time of plastic deformation is short.

Interface microstructure and bond strength of 1420/7B04 composite sheets prepared by diffusion bonding

The effect of temperature on interface microstructure and shear strength of 1420 A1-Li alloy and 7B04 A1 alloy composite plates prepared by diffusion bonding were investigated. The results indicate the optimum temperature for bonding the composite plates is 520℃, a sound bonding interface without continuous intermetallic compound layers and interfacial voids is obtained, and the shear strength value of bond joints can be as high as 190 MPa. An interfacial transition zone is formed due to the alloying elements mutual diffusion during the bonding process. Meanwhile, the effect of temperature on diffusion of alloying elements and interface reaction were discussed in detail, the results show that the higher temperature can increase the diffusion of alloying elements fluxes across the bonding interface, which can accelerate the closure of interfacial voids; meanwhile, when Mg atoms diffuse across the bonding interface, it can react with and break up the surface oxide films into discrete particles, and the removal of interface oxides increases the metal to metal bond areas and improves the bond quality.

Atom Diffusion Behavior and Bonding Strength of Ag/Cu Composite Interface

The atom (Ag,Cu) diffusion behavior and the effect of technology on the interface of rolled Ag/Cu composite contact were investigated. The concentration of Ag and Cu atoms near the interface was determined with electron probe. The bonding strength of composite interface was tested and the fracture in tensile sample was observed by SEM. The results show that there was inter diffusion of Ag and Cu atoms on the interface, which formed compact layer with high bonding strength of 98 MPa. The practical application proved that the Ag/Cu composite interface is reliable.

Interfacial reactions and diffusion path in partial transient liquid-phase bonding of Si_3N_4/Ti/Ni/Ti/Si_3N_4

The interfacial reactions in partial transient liquid-phase bonding of Si3N4 ceramics with Ti/Ni/Ti interlayers were studied by means of scanning electron microscopy （SEM）, energy dispersive spectrometry （EDS） and X-ray diffractometry （XRD）. It was shown that the interfacial structure of Si3N4/TiN/Ti5Si3+Ti5Si4 + Ni3Si/ （NiTi ） /Ni3Ti/ Ni was formed after bonding. The activation energies for TiN layer and the mixed reaction layer of Ti5Si3 + Ti5Si4 + Ni3Si are 546. 8 kJ/mol and 543. 9 kJ/mol, respectively. The formation and transition processes of interface layer sequence in the joint were clarified by diffusion path. An important characteristic, which is different from the conventional brazing and soid-state diffusion bonding, has been found, i. e., during the partial transient liquid-phase bonding, not only the reaction layers which have formed grow, but also the diffusion path in the subsequent reaction changes because of the remarkable variation of the concentration on the metal side.

Microstructure and properties at bonding interface of AA4045/AA3003 aluminum alloy cladding billet prepared by semi-continuous casting

AA4045/AA3003 cladding billet was prepared by direct chill semi-continuous casting process. The macrostructures, microstructures, temperature distribution, compositions distribution and the mechanical properties at the bonding interface were investigated in detail. The results show that the cladding billet with few defects could be obtained by semi-continuous casting process. At the interface, diffusion layer of about 10μm on average formed between the two alloys due to the diffusion of alloy elements in the temperature range from 596 to 632 °C. From the side of AA4045 to the side of AA3003, the Si content has a trend to decrease, while the Mn content has a trend to increase gradually. Tensile strength of the cladding billet reaches 103.7 MPa, the fractured position is located on the AA3003 side, and the shearing strength is 91.1 MPa, revealing that the two alloys were combined metallurgically by mutual diffusion of alloy elements.

Diffusion Bonding of Dissimilar Intermetallic Alloys Based on Ti_2AlNb and TiAl

Direct diffusion bonding of an orthorhombic Ti2AlNb base alloy to a TiAl base alloy, Ti-22Al-23Nb-2Ta and Ti-46.2Al-2Cr-2Nb-0.15B （at. pct）, was carried out and the interface microstructure, formation of new phase at the interface and joint strength were characterized. At low temperature, a new phase with AlNb2-structure, Al（Nb, Ti）2, was formed in the interface region adjacent to the O base alloy. The α2 was found to be the major reaction product and developed in the interface region adjacent to the TiAl alloy as well as in the region adjacent to the O base alloy accompanying the formation of Al（Nb, Ti）2. The occurrence of Al（Nb, Ti）2 has been attributed to the different diffusivity of Nb and Al, leading to a eutectoid-like reaction. At relatively high temperature, Al（Nb, Ti）2 did not form due to enhanced diffusion of Nb but a B2-enriched zone formed on the O alloy side instead after long holding time. Only when an appropriate interface microstructure was achieved by optimizing the bonding parameters, could the shear strength of the joint reach 80% of that of the TiAl base alloy.

Effect of bonding temperature and heat treatment on microstructure and mechanical property of Mg−6Gd−3Y alloy vacuum diffusion bonded joints

Diffusion bonding of as-cast Mg−6Gd−3Y magnesium alloy was carried out at temperatures of 400−480℃ with bonding pressure of 6 MPa for 90 min.Diffusion bonded joints were solution treated at 495℃ for 14 h and then aged at 200℃ for 30 h.Microstructures and mechanical properties of joints were analyzed.The results showed that rare earth elements and their compounds gathering at bonding interface hindered the grain boundary migration crossing bonding interface.Tensile strength of as-bonded and as-solution treated joints increased firstly and then decreased with the bonding temperature increasing due to the combined effects of grain coarsening and solid-solution strengthening.As-bonded and solution-treated joints fractured at matrix except the joint bonded at 400℃,while aged joints fractured at bonding interface.The highest ultimate tensile strength of 279 MPa with elongation of 2.8%was found in joint bonded at 440℃ with solution treatment followed by aging treatment.

Evolution of bonding interface in solid-liquid cast-rolling bonding of Cu/Al clad strip

Cu/Al clad strips are prepared using solid?liquid cast-rolling bonding(SLCRB)technique with a d160mm×150mm twin-roll experimental caster.The extent of interfacial reactions,composition of the reaction products,and their micro-morphology evolution in the SLCRB process are investigated with scanning electron microscope(SEM),energy dispersive spectrometer(EDS),and X-ray diffraction(XRD).In the casting pool,initial aluminized coating is first generated on the copper strip surface,with the diffusion layer mainly consisting ofα(Al)+CuAl2and growing at high temperatures,with the maximum thickness of10μm.After sequent rolling below the kiss point,the diffusion layer is broken by severe elongation,which leads to an additional crack bond process with a fresh interface of virgin base metal.The average thickness is reduced from10to5μm.The reaction products,CuAl2,CuAl,and Cu9Al4,are dispersed along the rolling direction.Peeling and bending test results indicate that the fracture occurs in the aluminum substrate,and the morphology is a dimple pattern.No crack or separation is found at the bonding interface after90°-180°bending.The presented method provides an economical way to fabricate Cu/Al clad strip directly.

Study on Interfacial Bonding State of Ag-Cu in Cold Pressure Welding

The interfacial bonding of Ag-Cu (they are limited soluble) formed by the technology of cold pressure welding was discussed from the point of metallurgic view in this paper. Meanwhile, tensile test and microscopic test were adopted for studying the state of interfacial bonding, suggesting that the joint of Ag-Cu has not only strong welding joint but also atomic diffusion on the interface. For Ag-Cu, the interaction of dislocation caused by plastic deformation will cause the strain and the vibration of microconstructer defects, accompanied by emitting energy. The energy increases the atomic action and the amplitude of atomic vibration, and the result is that the atom can diffuse to several lattice parameters deep from interface to inner metals. Therefore, under the condition of chemical potential gradient, the special technique, cold pressure welding rather than basic requirements of diffusion should be taken into account. During the cold pressure welding, plastic deformation plays an important role for it causes the metals′ displacement, crystal defects, further activates the surface atoms. Finally, the fracture of atomic bonding leads to the atomic exchange and diffusion between the new metals′ surfaces.In other words the metals Ag,Cu can achieve solidate bonding by cold pressure welding accompanied by the atomic diffusion. Moreover, theoretical analysis and calculation on the basis of thermodynamics, crystallogy, so- lid physics,etc, have been applied to calculate the amount of atomic diffusion, which has further proved the testing results that joint Ag-Cu has strong bonding strength through the mechanism of atomic diffusion.

Characteristics of deformation joining of aluminum-stainless steel composite sheet

In order to study the characteristics of deformation joining of aluminum-stainless steel composite sheet, an applied example of this composite sheet was given. The conditions of the composite sheet were discussed, the optical micrographs and scanning electron micrographs were examined by contrast ways of deformation joining and braze joining. Simultaneously the analysis of energy spectrum was also conducted. The results indicate that the deformation joining composite sheet possesses high bonding strength, good corrosion resistance, less inclusions and less microcracks.

316L不锈钢扩散焊接头组织性能分析

印刷电路板式换热器具有多层薄壁、微通道的结构,如何实现其高质量连接的问题亟待解决.316L不锈钢因其优异的力学性能、焊接性能与耐腐蚀性能,常用于印刷电路板式换热器的制造.文中采用真空扩散连接的方法实现了316L奥氏体不锈钢的连接,并探究了最优工艺参数,建立了工艺参数—界面组织—力学性能之间的关系.结果表明,随焊接温度升高和保温时间的延长,接头焊合率、变形率上升,晶粒尺寸增长,硬度下降,抗拉伸剪切强度先升高后降低.1000℃–60 min–10 MPa为最优参数,此时接头抗剪强度最高,为626 MPa.该参数下的断裂方式为塑性断裂,断口呈典型的韧窝花样.创新点:(1)明确了316L不锈钢真空扩散连接的最佳工艺参数.(2)明确了焊接温度和保温时间对316L不锈钢真空扩散连接显微组织、力学性能的影响规律.

TiAl/40Cr扩散连接接头的界面结构及相成长

在 1173～ 1373K、0 .3～ 5 .4ks的接合条件下对TiAl金属间化合物与 4 0Cr钢进行了真空扩散连接。采用扫描电镜 (SEM )、电子探针微区成分分析 (EPMA)、X射线衍射分析 (XRD)等方法确定了反应相的种类和界面结构。研究结果表明 ,在 1373K的接合温度下 ,TiAl/ 4 0Cr接头生成了TiC ,Ti3 Al,FeAl和FeAl2 4种反应相 ,形成了 3个反应层 ,界面结构为TiAl/Ti3 Al+FeAl+FeAl2 /TiC/脱碳层 / 4 0Cr钢。界面总反应层的厚度随接合温度和接合时间按抛物线方程成长 ,成长的活化能Q为 2 11.9kJ/mol,成长常数k0 为 4 .6× 10 -5m2 /s。当脆性反应层厚度为 3μm时 ,TiAl/ 4 0Cr钢接头的室温拉伸强度达到 183MPa的最大值。

钛-钢扩散复合界面组织与结合强度

将钛管、钢管利用冷拔-内压扩散法制备了内包覆钛-钢复管。用扫描电镜、能谱分析、X-光衍射和拉剪试验等方法,研究了扩散退火温度与时间对钛-钢扩散复合界面附近组织、成分和界面剪切强度的影响。结果表明,该制备方法可使钛-钢实现冶金结合;界面剪切强度随扩散温度升高先增加后减小;750-800℃×0.5h扩散退火界面剪切强度最高,可达210MPa左右;扩散退火中Fe、Ti原子发生了互扩散;界面上有TiC形成:750℃×0.5h扩散退火试样断口未检测到TiFe、TiFe2相;900-950℃×0.5h扩散退火钢侧出现柱状晶区,钛侧出现无晶界晶区与针状马氏体晶区。

用Fe-Ti合金扩散连接SiC陶瓷

利用Ｆｅ－Ｔｉ合金在１４７３～１７２３Ｋ、０．９～５．４ｋｓ的接合条件下对常压烧结ＳｉＣ陶瓷进行了真空扩散连接，接头中形成ＴｉＣ、ＦｅＳｉ、Ｔｉ５Ｓｉ３反应相。试验结果表明，用Ｆｅ－５０Ｔｉ（ａｔ％）合金，在１６２３Ｋ、２．７ｋｓ的接合条件下，接头的高温（９７３Ｋ）剪切强度达到１３３ＭＰａ。

SiC/Nb/SiC扩散连接接头的界面构造及接合强度

使用Ｎｂ箔作中间层对常压烧结ＳｉＣ陶瓷进行了真空扩散连接。在最初的反应阶段，六方晶的Ｎｂ２Ｃ和Ｎｂ５Ｓｉ３Ｃｘ反应物分别在Ｎｂ和Ｓｉ侧形成。随着连接时间的增加，立方晶的ＮｂＣ和六方晶的ＮｂＳｉ２相在界面出现。试验结果表明，在１７９０Ｋ、３６ｋｓ的连接条件下所获得的接头，其室温剪切强度达到１８７ＭＰａ，高温（９７３Ｋ）剪切强度超过１５０ＭＰａ。

用中间层为非活性金属FeNi/Cu的Si_3N_4陶瓷与Ni的扩散连接

采用非活性金属中间层FeNi/Cu在高、低真空条件下进行了Si3 N4 陶瓷与Ni的扩散连接 ,然后对部分接头进行了热等静压 (HIP)后处理 ,测定了连接接头的四点弯曲强度 ,用扫描电镜 (SEM)、电子探针 (EPMA)和X射线衍射仪 (XRD)对连接界面区域进行了分析。结果表明 ,采用非活性金属中间层扩散连接Si3 N4 陶瓷与Ni,在高真空和低真空条件下均能获得高强度连接 ,连接界面处没有形成Ni-Si化合物反应层 ,连接时间对接头强度的影响不明显。上述特征与用活性金属中间层连接时的情况截然不同。本文的连接方法有着重要的工程应用前景。

碳化硅陶瓷和金属铌及不锈钢的扩散接合

研究了碳化硅陶瓷和金属Nb的相反应、显微组织结构和Nb2C、Nb5Si3Cx、NbC及NbSi2的形成过程。分析了反应相对接头强度的影响。试验结果表明，SiC／Nb／SiC、SiC／Nb和SiC／Nb／SUS304接头的剪切强度分别达到了187MPa、100MPa和120MPa。

Ti/Cu/Ti部分瞬间液相连接Si_3N_4的界面反应和连接强度

用Ti/Cu/Ti多层中间层在 12 73K进行氮化硅陶瓷部分瞬间液相连接 ,实验考察了保温时间对连接强度的影响。用SEM ,EPMA和XRD对连接界面进行微观分析 ,并用扩散路径理论 ,研究了界面反应产物的形成过程。结果表明 :在连接过程中 ,Cu与Ti相互扩散 ,形成Ti活度较高的液相 ,并与氮化硅发生反应 ,在界面形成Si3N4 /TiN/Ti5Si3+Ti5Si4 +TiSi2 /TiSi2 +Cu3Ti2 (Si) /Cu的梯度层。