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Authors: Vinzenz Bissig, Jolanta Janczak-Rusch, Matteo Galli
Abstract: Three different approaches for metal to ceramic brazing are compared using the example of Si3N4/TiN-steel joints: the use of an active filler metal (single layer brazing system), the metallisation of the ceramic and brazing with a non active filler (two-layer brazing system), the use of a composite brazing filler system (three layer brazing system). Different aspects are analysed: the development of the joint’s microstructure in the as-brazed state, the thermally induced residual stresses and the resulting bend strength of the joint’s strength. With two layers and three layers brazing system, bend strength of about 400 MPa, about 15% higher then single filler metal, were achieved. The three layer brazing system has two advantages: firstly one step processing secondly lower scattering of joint bend strength compared to two layers brazing system. The key factors in all cases are the selection of the brazing fillers and the braze design. In all cases a careful selection of the brazing fillers and the braze design are the key factors. The first criteria for the selection of the brazing fillers for joints of dissimilar materials can be done by considering only the main filler characteristics like titanium content, processing temperature and yield stress. It’s necessary to simulate the joint behaviour by finite element simulation for verifying the final selection of filler metals. It was clearly seen that the plasticity of the filler metal is the main factor affecting residual stresses for the joint geometry in this current work.
Authors: Manuel Marya, M.J. Rathod, Surendar Marya, Muneharu Kutsuna, Didier Priem
Abstract: Laser-roll bonding and magnetic pulse welding are two relatively new processes that greatly minimize problems of metallurgical incompatibilities between dissimilar metals and alloys. These two processes, though technologically apart and invented for components with distinct geometries, utilize to various extents high pressures to facilitate rapid and localized interfacial heating and create reliable joints. In this paper, relations between process parameters, microstructures, and properties are discussed for aluminum-to-steel joints made by laser-roll bonding and magnetic pulse welding.
Authors: Tung Han Chuang, Shiu Fang Yen
Abstract: In this study, 0.1~1.0 wt.% of pure Ce was added into a Sn3Ag0.5Cu solder alloy, resulting in the formation of precipitated CeSn3 clusters of a size greater than 20 1m in the reflowed solder matrix. After natural aging at room temperature for more than 3 days, oxidation on the surface of the CeSn3 clusters was much heavier than in the undoped Sn3Ag0.5Cu solder matrix. In addition, many tin whiskers with a diameter of about 0.1 to 0.3 μm had been squeezed out of the oxide layer of the CeSn3 precipitates. The increase in aging time at room temperature causes the tin whiskers to grow rapidly. The whiskers can grow even to a length of over 300 μm after 21 days of storage. The whisker growth rate in one particular case reached 8.6Å/s after room temperature storage for only one day. The whiskers formed during storage at a higher temperature (1500C have a coarse diameter of 1 to 3 μm. In some cases, high temperature storage results in the formation of short whiskers in a hillock shape with a diameter of about 5 to 10 μm.
Authors: David G. Richards, Philip B. Prangnell, Philip J. Withers, Stewart W. Williams, Andrew Wescott, E.C. Oliver
Abstract: Although Friction Stir Welding (FSW) avoids many of the problems encountered when fusion welding high strength Al-alloys, it can still result in substantial residual stresses that have a detrimental impact on service life. An FE model has been developed to investigate the effectives of the mechanical tensioning technique for controlling residual stresses in FSWs. The model purely considered the heat input and the mechanical effects of the tool were ignored. Variables, such as tensioning level, heat input, and plate geometry, have been studied. Good general agreement was found between modelling results and residual stress measurements, justifying the assumption that the stress development is dominated by the thermal field. The results showed a progressive decrease in the residual stresses for increasing tensioning levels and, although affected by the heat input, a relatively low sensitivity to the welding variables. At tensioning levels greater than ~ 50% of the room temperature yield stress, tensile were replaced by compressive residual stresses within the weld.
Authors: Y. Miyazawa, C.S. Chang, H. Sato, Jun Suda, T. Hiraoka, Kiichi Kanda, T. Ariga
Abstract: Joining technology of CP-Titanium and Titanium alloy is very important for manufacturing field. In that case of titanium brazing, chemical compositions of brazing filler metal and brazing atmosphere are very important. In this study, CP-Ti/CP-Ti and Ti alloy/Stainless Steel were brazed with Ti-based laminated brazing filler metal by using continuous type furnace under Ar gas atmosphere containing extremely low oxygen. Laminated filler was fabricated by roll bonding technology. Chemical compositions of laminated filler metal used in this study were Ti-15Cu-15Ni and Ti-20Zr-20Cu-20Ni. Brazing temperature employed in this study was 850, 900, 950, and 1000 C. These brazing temperatures were based on thermal analysis results and alpha-beta transformation temperature of the base metal used in this study. Firstly melting properties of laminated brazing filler metal was investigated with DTA and DSC. Secondary joint characteristics were estimated by micro-structural observation at the joint and mechanical properties measurement. Sound joint was obtained in this study according to outside appearance of the specimen. Ti-20Zr-20Cu-20Ni filler had low melting point as compared with Ti-15Cu-15Ni according to thermal analysis results and fillet form-ability. Ni and Cu were diffused from molten brazing filler to base metal during brazing and Ti-Cu-Ni eutectoid reaction was took placed at the based metal during cooling after brazing.
Authors: C. Huang, G. Cao, S. Kou
Abstract: Liquation cracking in the partially melted zone (PMZ) of aluminum welds was studied. The PMZ is the region immediately outside the fusion zone where the material is heated above the eutectic temperature. Highly crack-susceptible alloys 2024 and 7075 were welded using gas-metal arc welding (GMAW) with filler metals 1100 and 4043, respectively. Circular-patch welds were made on 3.2 mm thick workpiece with full penetration, and single-pass welds were made on 9.5 mm thick workpiece with partial penetration. Liquation cracking was observed in all welds. Dualpass welds were also made on 9.5 mm thick workpiece, with overlapping between the penetration tips of the two partial-penetration passes made on the opposite sides of the workpiece. Liquation cracking was found in the first pass but not in the second pass. The results were explained using TfS (temperature vs. fraction solid) curves of the weld metal (WM) and the PMZ based on the following criterion proposed recently: liquation cracking can occur if WM fS > PMZ fS during PMZ solidification.
Authors: Shi Quan Zhou, Hong Zhao, Qiang Dong
Abstract: Affection of the main process parameters(Temperature and Time) on microstructure and properties of Ti(C,N)/Ni interface has been studied by using Cu and Nb interlayer in Vacuum diffusion welding device. Results have shown that interface interlayer did not change and interface microstructure was Cu/Nb layer structure and Cu diffused into Ni with a little when diffusion welding temperature was lower than 1273K. But when diffusion welding temperature was 1523K, interface microstructures were Ni8Nb metallic compound and dispersing deposition CuNi solid solution in the earlier, finally they were transformed into (Ti,Nb)(C,N)+Nb7(Ni,Ti,Cu)6+NbNi3 near Ti(C,N) and NiCu+NbNi8 near Ni. It was clear that Cu was as transition liquid which dissolved Ni so as to forming CuNi transition liquid, so that Nb was dissolved in CuNi transition liquid rapidly. Ti(C,N) can been wetted with creating NiNbCu transition liquid, and then, a little (Ti,Nb)(C,N) solid solution were formed at interface so as to increasing interface combining capability. Interface shear strength may get to 140 MPa.
Authors: Jie Zhang, Lin Bin Zhu, Bao You Zhang, Shi Wei Yang
Abstract: Si3N4 and 40CrMo steel was joined using Ag-Cu-Ti-Pd brazing filler. Microstructure of the joint and bonding interface was studied by SEM and EDS, and the phase structure was analyzed by XRD. The results indicate that reaction layers at ceramic/ filler alloy and filler alloy/steel interfaces are formed. There is a reaction layer containing TiN and Ti5Si3 between ceramic and filler alloy, while the reaction layer between filler alloy and steel is composed of Fe-Ti compound. The middle part of the joint is an eutectic structure composed of Ag-riched and Cu-riched solid solutions. With the increase of the brazing temperature, the thickness of the joint seem decrease, the thickness of the reaction layer between Si3N4 and filler alloy increases and then decreases, and the thickness of the reaction layer between filler alloy and steel increases.
Authors: Kazuyoshi Saida, Woo Hyun Song, Kazutoshi Nishimoto
Abstract: The diode laser brazing of heat-resistant alloys with precious brazing filler metals has been conducted using the tandem beam consisted of preheating beam and main brazing beam. The 1mm thick plates of Inconel 600 and A286 alloys were butt-brazed with the 0.5mm diameter Au-18%Ni, Ag-10%Pd and Ag-21%Cu-25%Pd filler metals using a brazing flux. The sound butt joints which were free from brazing defects such as porosity and lack of penetration could be obtained at the brazing clearances of 0.1-1.5mm. Fracture strength of braze joints using Au-Ni and Ag-Cu-Pd filler metals was comparable to the base metal strength at any brazing clearance between 0.1-1.5mm, whereas that using Ag-Pd filler metal increased with decreasing the brazing clearance and attained about 70% of the base metal strength at brazing clearance of 0.1mm. The computer simulations of the braze metal flowing and the base metal erosion suggested that the preheating effect during the tandem beam brazing resulted in the superior brazability at the narrow-gap as well as wide-gap brazing attributed to the improvement in the wetting, spreading, infiltrativity and the erosion resistance of melted filler metal.
Authors: Janez Tušek, B. Taljat, Marco Hrženjak, Damjan Klobčar
Abstract: The paper treats the application of laser to repair of cracks occurring at dies for die casting of non-ferrous metals (particularly aluminium, magnesium and their alloys). The first part describes a suitable laser unit enabling crack grooving and then welding. An Nd:YAG laser source is shown with its equipment for laser-beam transfer, control and directing of laser-beam focus. Dies for die casting are made of quality steels and are of very complex shape. As far as their repair is concerned this means that they are to be welded at their edges, corners, narrow gaps and vertical walls, i.e. in various positions and in various directions. In the second part the grooving technology is described, and in the third part laser welding of grooved cracks using a filler material, i.e., a thin welding wire. At the end some conclusions are drawn. It is stated that from the viewpoints of technology and economics, it is sensible to laser groove and then weld the thermal cracks with a suitable material. The filler material should have such a chemical composition that after welding a weld having adequate mechanical properties, without any additional heat treatment, is obtained.

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