Papers by Keyword: Diffusion Bonding

Abstract: The study is diffusion bonding of Mg-AZ31 and Al-6061 under pressure and no pressure by using the direct bonding method. After bonding process, characteristics phase in interface and bonding boundaries of Mg-AZ31/Al-6061 were characterized . The diffusion formation was observed by SEM. Aluminum solid solution and Mg₁₇Al₁₂ alloy phase was proved by analysis of XRD. In the process of measurement, crystalline structure of nearby interface characteristics phase was analyzed in detail by TEM. Based on the above analysis, the crystal model of the magnesium alloy and aluminum alloys was established under pressure, and the bonding mechanism was discussed. The results show that the bonding materials could be bonded under no pressure and the structure of bonding interface is more optimized than pressure.

Abstract: The direct diffusion bonding of TiAl-based intermetallics and the diffusion bonding of TiAl-based intermetallics with hydrogenated Ti6Al4V alloys interlayer containing 0.5wt% hydrogen were carried out. The effects of hydrogen on diffusion bonding were investigated by SEM, EPMA, XRD, TEM and TG/DSC. The good joint was formed at 850°C for 15 min under a pressure of 15MPa at the diffusion bonding of TiAl-based intermetallics with hydrogenated Ti6Al4V alloy interlayer containing 0.5wt% hydrogen, and the room temperature shear strength was up to 290MPa. Relatived to direct diffusion bonding of TiAl-based intermetallic, the bonding parameters decreased prodigiously. According to the experimental observations, the Ti6Al4V alloy hydrogenated 0.5 wt% consisted of close-packed hexagonal structure α′ martensite phase, face-centered cubic structure of δ-phase, α and βH structure. The lamellar δ hydride and βH phase disappeared after bonding, and the lamellar (α+β) structure were formed. Because of the dehydrogenation during bonding, metastable hydride containing low hydrogen appeared. The remaining hydrogen in Ti6Al4V alloy at high temperatures enhanced the capacity of the plastic deformation and the diffusion ability of the alloy elements, which helped to improve the spread of the atom.

Abstract: The solid-state diffusion bonding experiments of high Nb containing TiAl alloy were successfully carried out at 950°C under a uniaxial pressure of 30MPa for 45min, and the influence of different initial microstructures, such as initial forged microstructure (named duplex microstructure) with different grain sizes, near lamellar microstructure and full lamellar microstructure, on the interface of the bonding joints were investigated. And the microstructure characterization of interfaces was taken by OM, SEM, EDS and micro-hardness tester. The results indicated that the grain size and strain energy are of great importance to improve the quality of interfacial bonding. Besides, the interfacial microstructure was found different from matrix and changed during the diffusion bonding process. Meanwhile, micro-hardness tests of the three kinds of joints showed that the micro-hardness in the interface was slightly higher than matrix in all the joints, resulted from the working hardening of the interface under the uniaxial pressure.

Abstract: Cu and Al6061 alloys were diffusion-bonded at 530°C with Cu-15 wt. % Ag alloy as an intermediate layer and the interface microstructure were analyzed. The presence of Cu₉Al₄, CuAl and CuAl₂ intermetallic layers were confirmed along with Ag₃Mg and AgMg intermetallics. Ag was found to diffuse into Al, forming needle-shaped Ag₂Al precipitates in Al substrate close to Al/Cu-Ag interface region. Micro-Vickers indentation aimed at the interface regions, CuAl/CuAl₂ and CuAl₂/Ag₃Mg-AgMg lamella revealed that cracks were formed mostly around the indenter mark in CuAl₂ layer more than in CuAl and no cracks in the Ag₃Mg-AgMg lamella region, suggesting CuAl₂ is more brittle than CuAl and Ag₃Mg-AgMg lamella is rather ductile. Ag₃Mg-AgMg lamella was found to be formed at the interface between Al and CuAl₂. The formation of ductile Ag₃Mg-AgMg lamella at the Al interface suggests that the diffusion bonding Cu and Al with Cu-Ag or Ag as a intermediate layer may increases the interface reliability of Cu/Al hybrid alloy.

Abstract: The objective of this work was to study various aspects of liquid state diffusion bonding of cylindrical samples of Al₂O₃ and commercially pure niobium (99.7%) by brazing using a 25 µm thick 70Cu-30Zn (wt%) alloy as joining element. Initially, sintering of alumina powder was carried out in order to produce a 7 mm diameter samples at 1550°C by 120 minutes. Joining experiments were carried out on Al₂O₃/Cu-Zn/Nb/Cu-Zn/Al₂O₃ sandwich-like combinations at temperature of 920°C, 950°C and 980°C using different holding times under argon (Ar) atmosphere. The experimental results show a successful joining of alumina to niobium at 950°C and 980°C, however not at 920°C. Joining of Al₂O₃/Cu-Zn/Nb/Cu-Zn/Al₂O₃ occurred by the formation of a homogeneous diffusion zone with no interfacial cracking or porosity at the interface. Scanning electron microscopy (SEM) micrographs show the layer formed in the reaction zone. It was observed that the width of the reaction zone increases with bonding temperature and time. Electron probe microanalysis (EPMA) revealed that at any particular bonding temperature, Nb travel into the Cu-Zn joining element forming a circular precipitate phase near to the alumina ceramic.

Abstract: This paper studies mainly the diffusion bonding of 3Y-TZP/SUS304 by using the chemical bonding method. In the bonding interface of 3Y-TZP and SUS304, the Ti-Cu powder/sheet was used as bonding materials. In bonding process, multi-alloy with Fe-Ti and Fe-Cu have been confirmed by Electron Probe Micro-Analyzer (EPMA) determination. Through the microstructure observed by AFM and SEM, bonding boundaries of 3Y-TZP/SUS304 by Ti-Cu powder/sheet had good formation. The distribution of the residual stress on near interface was measured by XRD method. By using of these results, the mechanism of the ceramic and stainless steel was discussed.

Abstract: This paper is mainly a study the diffusion bonding of Mg-AZ31/Al-6061 by using the direct bonding method. After bonding process, multilayer field with Mg-Zn and Al-Zn have been confirmed by EPMA determination. Through the microstructure observed by SEM, bonding boundaries of Mg-AZ31/Al-6061 had good diffusion formation. The identification of the component on near interface was measured by XRD method. By using of these results, the mechanism of the magnesium alloy and aluminum alloys was discussed.

Abstract: The influence of laser remelting on the mechanical property and fracture behavior of the superplastic diffusion bonding between TiAl intermetallics and TC4 alloy was investigated. The joint bonded by the pre-remelted samples displayed well diffusion, but the mechanical properties of the joint should be further enhanced. The mechanical properties of the joint pre-remelted under the diffusion bonding conditions of 915/80MPa/1h are lower than that of the joint without remelting. After the heat treatment on pre-remelted joint sample at 860, the mechanical properties have been enhanced greatly.

Abstract: A copper rod/FeSiB amorphous ribbon/copper rod sandwich laminated composite material has been successfully fabricated by co-pressing at temperatures within supercooled liquid region. The bonding interface has been characterized by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Results showed that a good bonding interface could be obtained only when the initial surface were carefully polished. The diffusion zone confirmed by EDS is about 60nm, indicating the bonding is in atomic metallurgical level via limited diffusion. The present results show that even the diffusion length is very small, diffusion bonding in the supercooled liquid region could be an effective way for fabricating Fe-based metallic glass/Cu laminated composites

Abstract: The diffusion bonding of 316L stainless steel with Ni interlayer in the temperature range of 850-1050°C, under a uniaxial pressure 10 MPa for 60 min is investigated. The diffusion bonds have been evaluated light microscopy, SEM, X-ray diffraction and tensile test. The main result is that the introduction of the interlayer may reduce the room temperature strength but increase the high temperature strength. This is attributed to the transformation of Fe_0.64Ni_0.36 formed in bonding process into FeNi₃ at high temperature. Kirkendall voids are formed in the Ni interlayer near the interface where the specimen fractured. Fractographic study indicates that the fracture mode of the joints is strongly affected by the bonding and testing temperature. The fracture is a mixed mode of brittle and ductile fracture in high temperature tensile test, while it is brittle fracture at room temperature.