Microstructural characteristics in Ni/zirconia bonding

Zirconia with various dopants of Y₂O₃ and CeO₂ was employed in the solid state bonding of an Ni/ceramic assembly. The interfacial microstructure of the bonding assembly was examined by electron microscopy and X-ray diffraction and the bonding strength was evaluated with a tensile test under constant pressure. An intermediate layer was observed in the interface of the 3Y₂O₃-10CeO₂-ZrO₂/Ni bonding assembly which revealed that the solid state bonding of Ni/zirconia required the formation of a thin oxide layer to wet the ceramics. In the Ni/zirconia bonding, the growth of NiO was influenced by the dopants in the zirconia. This would, in turn, result in different bonding strengths between ZrO₂ and nickel. The highest bonding strength occurred in the 12CeO₂-ZrO₂/Ni assembly.     

Diffusion bonding of zirconia to silicon nitride using nickel interlayers

The possibilities of diffusion bonding of zirconia to silicon nitride using a nickel interlayer were studied by carrying out bonding experiments under various processing conditions. The process parameters considered were temperature, bonding pressure and interlayer thickness. The optimal process conditions were determined by evaluating the mechanical strength using shear strength testing. It was found that the bonding is optimal in the temperature range 1000–1100°C. The bond strength appears to be independent of the bonding pressure and interlayer thickness if threshold values are exceeded (bonding pressure >14 MPa, interlayer thickness >0.2 mm). At the Si3N4 Ni interface, Si3N4 decomposes, forming a solid solution of silicon in nickel. At the ZrO2–Ni interface, no reaction was observed. © 1998 Kluwer Academic Publishers     

Heat-resistant joints of Si3N4 ceramics with intermetallic compounds formed in situ

The possibility of the improvement on the heat resistance of Si₃N₄ ceramic joints with intermetallic compounds formed in situ was investigated. The Si₃N₄ ceramics were joined with Ti/Ni/Ti multi-interlayers between 1000 and 1150°C. The effects of various parameters, which include the thickness of Ti and Ni foils, the pressure imposed during bonding, the bonding temperature and the holding time, on the microstructures and the strength (both at room temperature and at high temperature) of the joints were studied. The results indicated that the sound joints with higher strength both at room temperature and at elevated temperature could be acquired with intermetallic compounds formed in situ under appropriate bonding parameters. The shear strength at 800°C could sustain about 88 MPa.     

Reactive brazing of ceria to an ODS ferritic stainless steel

This research study shows that a ceria ceramic can be bonded to an ODS ferritic stainless steel (MA956) by reactive brazing using a Ag₆₈-Cu_27.5-Ti_4.5 interlayer. The ability to join these materials provides an alternative to the current ceramic interconnects used in the development of solid oxide fuel cells. Initial results show that the ceramic-metal bonds survived the bonding process irrespective of the degree of porosity within the ceria ceramic. Metallographic analyses indicate that a reaction zone formed along the ceria/braze interface, which was not only titanium rich, but also consisted of a mixture of copper oxides. When the ceramic-metal bonds were exposed to high bonding temperatures or when subjected to thermal cycling at 700°C, this reaction layer increased in thickness and had a detrimental affect on the mechanical strength of the final joints.     

Liquid Phase Bonding of 316L Stainless Steel to AZ31 Magnesium Alloy

The excellent corrosion resistance,formability and strength make stainless steels versatile for diverse applications.However,its high specific strength and good crashworthiness make it suitable for transportation and aerospace industry.On the other hand,the need to reduce the weight of vehicle and aerospace components has created renewed interest in the use of magnesium alloys.Due to their differences in physical and metallurgical properties,bonding of the 316L steel and AZ31 magnesium alloy using conventional fusion welding methods encountered many limitations.Therefore,the use of liquid phase forming interlayers is required to overcome the differences in their properties,eliminates the need for a high bonding pressure to achieve intimate contact between the bonded surfaces.Both Cu and Ni interlayers successively formed a eutectic phase with magnesium.The formation of intermetallics and Mg diffusion caused the eutectic phase to isothermally solidify with increasing bonding time.The formation of ternary intermetallic phases(λ1 and B2) impaired the bond shear strength particularly at the end of the isothermal solidification stage where no eutectic phase was observed.However,the joints showed a higher shear strength value of 57 MPa when bonding with Cu interlayer at 530℃ for 30 min compared to 32 MPa when Ni interlayer was used at 510℃ for 20 min.     

面向超高温压力传感器的SiC-SiC键合方法

为了实现耐高温压力传感器SiC腔体的制作,分别利用高性能陶瓷胶、旋涂玻璃和金属Ni等3种材料作为键合层,研究了SiC-SiC键合工艺.扫描电子显微镜和键合拉伸强度实验结果表明,这3种材料的键合层均可以成功应用于SiC-SiC键合,其中高性能陶瓷胶键合层厚度为20~30μm,键合强度可达4 MPa;旋涂玻璃键合层厚度为2μm左右,键合强度约1.5 MPa;金属Ni键合层厚度为1μm,键合强度约为0.5 MPa.     

Effect of process parameters on semi-solid TLP bonding of Ti–6Al–4V to Mg–AZ31

The semi-solid transient liquid-phase bonding (Semi-solid TLP bonding) of titanium alloy Ti–6Al–4V to magnesium alloy Mg–AZ31 was performed using a eutectic forming nickel foil. The process parameters were optimized to achieve higher shear strength. The effect of temperature and pressure on microstructure evolution and mechanical characteristics were examined for bonding time between 5 and 60 min. Three reaction layers L1, L2 at Ni/Mg–AZ31 interface and L3 along the Ni/Ti–6Al–4V interface were determined within joint zone at a bonding temperature of 515 °C. The L1 and L2 reaction layers continued to be seen when the bonding temperature increased to 540 °C. When the bonding pressure increases from 0.2 to 0.7 MPa, a new reaction layer L4, at the Ni/Ti–6Al–4V interface was observed. The results showed that as the bonding time increased up to 60 min, the width of the joint decreased due to isothermal solidification. Maximum shear strength of 39 MPa was obtained for 540 °C and 0.2 MPa with a holding time of 20 min. However, further increase in bonding time to 60 min resulted in a decrease in shear strength to 8 MPa, and this decrease in strength was attributed to the increase in intermetallics forming within the joint zone.     

An investigation on diffusion bonding of aluminum to copper using equal channel angular extrusion process

A new method for production of bimetallic rods, utilizing the equal channel angular extrusion (ECAE) process has been introduced before by previous researchers, but no attempt has been made to assess the effect of different temperatures and holding times in order to achieve a diffusional bond between the mating surfaces. In present research copper sheathed aluminum rods have been ECAEed at room temperature and subsequently held at a constant ECAE pressure, at different temperatures and holding times to produce a diffusional bond between the copper sheath and the aluminum core. The bonding quality of the joints was examined by shear strength test and a sound bonding interface was achieved. Based on the results, a bonding temperature of 200 °C and holding time of 60-80 min yielded the highest shear strength value.     

Herstellung und Prüfung festkörpergeschweißter Keramik-Metall-Verbindungen

Preparation and Testing of Solid-State Bonded Ceramic-to-Metal-Joints Ceramic-to-metal joints were manufactured by solid-state bonding in a R. F.-high-vacuum apparatus. The influence of welding temperature, welding time and welding pressure on the bond strength was investigated for an alumina/niobium-combination consisting of a layered composite ceramic-metal foil-ceramic. As a measure of bond quality the fracture resistance K_ICV was chosen. K_ICV date were obtained by the use of 4-point bend tests and tensile tests. For comparison, data are presented concerning the fracture resistance K_IC of the bulk alumina and the conventional bond strength of the joints. In addition to the Nb/Al₂O₃-data, K_ICV factors are determined for other metal/alumina combinations and for a Zr/Si₃N₄ joint. The present solid-state bonding apparatus was used for the preparation of the specimens. A device for high-temperature bend testing in a high vacuum was constructed. Some data for the high-temperature bond strength of solid-state bonded joints are given.     

Effect of welding parameters on diffusion bonding of type 304 stainless steel–copper bimetal

Abstract

Stainless steel AISI type 304 and electrolytic cold rolled copper were joined by diffusion bonding at temperatures ranging from 650 to 950°C, for times from 5 to 45 min, and at pressures from 2 to 12 MPa. After bonding the microstructure of the interface was investigated, including the grain size, and shear and tensile strengths of the bonded specimens were determined. From the results, it was seen that the bond shear strength was dependent on interface grain boundary migration and on grain growth during the bonding process. In addition, attempts were made to find a relationship between grain size and shear strength in the bonding area. Taking into account the results of shear testing and microstructural observation, for a sound bond, optimum bonding conditions were obtained at temperatures of 800–850°C for 15–20 min at 4–6.5 MPa. The fracture behaviour of the diffusion bonded joint was investigated by means of shear and tensile testing under different bonding conditions. It was found that both shear and tensile strengths of the bonds were sensitive to the bonding conditions, and the intermetallic phases did not affect these parameters. Furthermore, the value of shear strength of the bond surface determined by shear testing was higher than the shear strength of the fracture surface determined by tensile testing.     

Interface reactions and bonding strength in aluminium alloy (AA-7075)-alumina diffusion bonds

Diffusion bonds between alumina and high-strength aluminium alloy (AA-7075) have been produced and studied in the present work. Direct diffusion bonding in the solid state was tested as a possible joining method for both materials. The nature of the AA7075-Al₂O₃ interface was investigated paying special attention to the chemical interaction processes between the alloying elements and the ceramic material, as well as their influence on the joint strength. SEM images and energy-dispersive microanalysis were used to determine the formation of reaction layer between both parent materials. Shear strength was used as an optimum method to evaluate the bond strength and the influence of the bonding parameters on it. A maximum shear strength of 60 MPa was achieved using bonding temperatures and pressures of 360 °C and 6 MPa, respectively, during very prolonged bonding times (100h). Fractographic studies of the failure surface gave additional information on those aspects.     

Activation energy of poly(methyl methacrylate) from rheometry and polymer welding

In this article, activation energies for a poly(methyl methacrylate) material were determined by shear rheometry and by bond strength in welding. Functions for temperature dependency of viscosity and for bond strength, depending on time and temperature, were found. These functions were fitted to measurements from shear rheometry between 230 and 270 °C and from strength of lap-shear joints welded from 105 to 130 °C, where by values of activation energies were found. It was found that bonding pressure was less than significant. Despite experimental differences, there was good correlation with data from literature for each method as well as for temperature dependency.     

The influence of brazing conditions on joint strength in Al2O3/Al2O3 bonding

The brazing of alumina ceramic to itself was performed using Ag₅₇Cu₃₈Ti₅ filler alloy. The bonding was carried out in a vacuum of 7 × 10^?3 Pa, and the joining conditions were at 1073, 1123, 1173, 1223, 1273 and 1323 K for 1.8ks under a pressure of 0.01 MPa, at 1123 K with a pressure of 0.01 MPa for 0, 0.3, 0.9, 1.8, 2.7 and 3.6 ks, and at 1123 K for 1.8 ks with pressures of 0, 0.01, 0.05, 0.10, 0.15, 0.20 and 0.30 MPa, to determine the effects of joining temperature, pressure and holding time on the joint strength. The joint strength was measured by shear tests. The interface microstructures and fractured surfaces after testing were observed by scanning electron microscopy (SEM). It was shown that the shear strength of Al₂O₃/Al₂O₃ joints was largely affected by the joining conditions; it first increased and then decreased with increasing joining temperature, pressure and holding time and depended mainly on the strength of interfacial reaction layer itself and the interface bonding strength between the reaction layer and the ceramic. The maximum joint strength was obtained when the reaction occurred under a suitable temperature, pressure and time, and the reaction layer thickness was about 2 μm. SEM observations revealed that there were four types of fracture and each kind corresponded to a different strength.     

Ceramic joining II partial transient liquid-phase bonding of alumina via Cu/Ni/Cu multilayer interlayers

Multilayer Cu/Ni/Cu interlayers that form a thin layer of a Cu-rich transient liquid phase have been used to join alumina to alumina at 1150 °C. The method and bonding conditions yield an assembly bonded by a Ni-rich (>94 at% Ni) interlayer at a temperature substantially lower than those normally required for solid-state diffusion bonding with pure Ni interlayers. Flexure strengths of as-bonded beams ranged from 61 to 267 MPa with an average of 160 MPa and a standard deviation of ±63 MPa. The highest flexure strengths were observed in samples where failure occurred in the ceramic. Post-bonding anneals of 10 h duration in air and gettered-argon at 1000 °C decreased the average room temperature strength to 138 and 74 MPa, respectively. In as-processed and annealed samples, varying degrees of interfacial spinel formation are indicated. Spinel formation may contribute to the scatter in as-processed samples, and the decrease in strength values resulting from annealing.     

Au/In等温凝固焊接失效模式研究

研究了Au/In等温凝固芯片焊接的失效模式,对每种失效模式的失效原因进行了讨论,并提出了相应的解决途径。结果表明：镀铟层过厚,会使焊层中产生Ni9In4相和大量空洞,导致焊层出现早期失效;焊接过程中芯片与衬底平行度不好,会使加载压力在焊区分布不均,并导致焊区局部区域发生Au/In不浸润;焊接温度过高,则焊层内会出现较大的热应力,可导致芯片或焊层开裂;在300℃高温下,由于过渡层Ni与Au/In相的反应,焊区内出现大量空洞,导致焊层剪切强度下降。对Au/In体系在未来高温电子器件芯片焊接中的应用,尚需寻找合适的过渡层材料。     

Diffusion bonding of TiAl using Ni/Al multilayers

With the stimulus of temperature and pressure Ni and Al can quickly react and produce the intermetallic compound NiAl. This reaction is highly exothermic and high temperatures can be attained in the surroundings. These characteristics make Ni/Al multilayers very attractive to technological applications as localised heat sources. In this study, Ni/Al multilayer thin films are used to promote bonding between TiAl intermetallic alloys. Ni and Al alternated nanolayers were deposited by d.c. magnetron sputtering onto TiAl samples, with periods of 5, 14 and 30 nm. Joining experiments were performed at 900 °C for 60 or 30 min, in a vertical furnace with a vacuum level better than 10⁻² Pa. Applied pressures of 5 MPa were tested. The microstructure of the cross-sections of the bond interface was analysed by energy dispersive X-ray spectroscopy and characterised by scanning electron microscopy. The observation of the microstructure for 14 and 30 nm period multilayers revealed sound bonding, while for 5 nm period porosity and cracks within the interlayer thin film were observed. The interface is divided into three distinct zones: one with columnar grains, another with very small equiaxed grains and the third with larger equiaxed grains. The joining process appears to depend on the diffusion of Ni and Ti across the interface and is assisted by the nucleation of nanometric grains at the interface. The mechanical strength of the joints was evaluated by shear tests. The bonds produced at 900 °C/5 MPa/60 min/14 nm exhibited the highest shear strength of 314 MPa.     

The effect of interlayer metals on the strength of alumina ceramic and 1Cr18Ni9Ti stainless steel bonding

The effects of interlayers of molybdenum and copper on the strength of alumina ceramic and 1Cr18Ni9Ti stainless steel bonding with Ag₅₇Cu₃₈Ti₅ filler metal were investigated. The interfacial morphologies were observed and analysed by scanning electron microscopy and energy dispersive X-ray (EDX) analysis, respectively. The joint strength was examined by shear tests. When using a molybdenum interlayer, the joint strength could be greatly improved because molybdenum not only reduced the interfacial residual stress, but also did not affect the interfacial reaction between the ceramic and the filler metal, and the maximum value was obtained when it was about 0.1 mm thick. When using copper as an interlayer, the joint strength was not increased but decreased, because copper reduced the activity of titanium in the filler metal, resulting in an insufficient interfacial reaction between the ceramic and the filler metal and the formation of poor interfacial adhesion. Therefore, in selecting an interlayer metal to reduce or avoid interfacial residual stress in joining ceramics to metals, in which the interfacial reaction of ceramic and filler metal is important to the joints, the interaction of interlayer metal and filler metal must be considered.     

Bond Strength of the Sn-Ti-Ⅹ Ternary Active Solders on Sialon Ceramic

The bond strength of the Sn based ternary active solders,Sn-5Ti with various contents of Ag,Cu,In,Ni or AI on sialon ceramic was investigated by the ceramic/ceramic joint joining.The bond strengthof Sn-STi (about 80 MPa) may increase to 90-100 MPa by small addition of Ag or Cu (about5-10%).A little Ni (about 1-3%) in the solder is slightly beneficial,but too more Ni (more than 5%)is harmful.Small addition of In is trivial,but too more In is detrimental.On the other hand,small addi-tion of AI in the active solder decreases greatly the bond strength of the solder,therefore it is veryharmful.In discussion,three suggestions for selection of the third element to increase the bondstrength of the soft solders on ceramic,i.e.with a high surface energy,benefiting to wetting on ce-ramic and strengthening the soft solder itself,have been made.     

料浆法氧化铝基陶瓷涂层的制备及性能研究

采用自制的磷酸铝粘结剂和一定比例的陶瓷骨料在1Cr18Ni9上用料浆法制备氧化铝基陶瓷涂层。试验结果表明：涂层较致密，涂层与基体结合强度较好；涂层可提高1Cr18Ni9钢在碱和盐溶液中的抗侵蚀能力。     

Joining of sialon ceramics by Sn-5 at % Ti based ternary active solders

The effect of a third element, such as silver, copper, indium, nickel or aluminium, on the joining of sialon ceramics with tin-5 at % titanium based ternary active solders was investigated. The content of the third element in the Sn-based solders was varied from 5–40% for Cu, from 5–10% for Ag and Al from 5–20% for In and from 1–5% for Ni. The joining was carried out in vacuum at 1100 K for 20 min. The four point bend testing of a butt joint of a ceramic/ceramic structure with dimensions 40 mm long, 3 mm wide and 4 mm high was used to study the bond strength between the ceramic and the Sn-based solders. The results show that the bond strength of the Sn-based solder with the sialon ceramic varied from 54–103 MPa. Small additions of Cu or Ag (about 5–10%), In (about 5–10%), or Ni (about 1–3%) to the solder is beneficial, but too much Ni (more than 5%) or In (more than 10%) is detrimental. On the other hand, Al in the active solder considerably decreased the bond strength of the solders with the ceramic. Suggestions are made for the selection of the third element in order to improve the bond strength of the soft solders with the ceramic. These include a high surface energy, improving the wetting of the solder on the ceramic and strengthening of the solder. This revised version was published online in November 2006 with corrections to the Cover Date.