Papers by Keyword: Diffusion Bonding (DB)

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Authors: Qing Sen Meng, Shao Ping Chen, Q.L. Wang, Z.A. Munir
Abstract: In this paper, the synthesis of four-layered functionally graded materials (FGMs) samples of (TiB2)pNi/(TiB2)p(Ni+Ni3Al)/ Ni3Al with different metallic substrate (Ni, Cu and Cr-Ni steel) by field-activated and pressure-assisted synthesis process (FAPAS) was investigated. It was shown that the imposition of the electric field and the combustion reaction of Ni3Al is the key for the successful synthesis of the FGMs during process. The exothermal reaction of the powder of nickel and aluminum during combustion enhanced the diffusion bonding in the interfaces subsequently. The microstructure, phase composition of the interfaces and mechanical properties of the graded materials were characterized, which showed indicative formation of firm bonds by the combustion reactive process. The samples have an excellent thermal shock resistance ability and gradient distribution of micro-hardness across the substrate layers and the surface layer.
Authors: S.A. Rizvi, T.I. Khan
Abstract: Nitinol (NiTi) shape memory alloys are widely used in a variety of biomedical applications, such as dental implants, cervical and lumbar vertebral replacements, joint replacements and stents. In this study, commercially pure Ti and Ni foils ~100 um thick were diffusion bonded in vacuum. The experimental conditions were optimized to achieve a near equiatomic composition to produce NiTi SMA thin foil of approx. 5-8 micron thick. The cross-sectional surfaces of joint were subjected to metallographic investigation using optical microscope after grinding, polishing and etching. Scanning electron microscope equipped with EDX system was utilized to characterize the bonded layer and compositional analysis. Differential scanning calorimetry (DSC) technique was employed to determine the shape memory effect. The samples were subjected to X-ray diffraction analysis in order to establish phase structures formed during the diffusion bonding stage. An ultra fast femto-second laser facility was utilized to ensure the production of complex shapes or patterns within micron scale.
Authors: A. Dixit, Mike Keavey, Alan Jocelyn, Jerome Way, Alexander Fanourakis
Abstract: Chemical cleaning has been used for several decades as a surface preparation technique for diffusion bonding. Here we present a theoretical investigation that examines the effect of changes in the process parameters when a laser is used as an alternative to chemical cleaning for surface contaminant removal. Here a theoretical model is described that includes laser beam attenuation in the plasma plume and its effect on evaporation of the material. Using the model, a comprehensive analysis of the effect of different fluences and other parameters for a KrF Excimer laser is presented. Calculations were carried out for a range of peak fluxes from below the ablation threshold to fluxes of the order of 9 x 1012 W/m2. The predicted effects on evaporation, melt depth and surface temperature are reported, illustrated by a number of surface topographic images from preliminary experiments. Finally, optimal parameters for cleaning according to the theoretical investigation are proposed.
Authors: Larry D. Hefti
Abstract: The Superplastically Formed and Diffusion Bonded (SPF/DB) titanium structure in production today for Boeing products, not including engines, are all diffusion bonded using matched metal tooling and are all fabricated using the common 6Al-4V alloy. The matched metal tooling concept presents a challenge in obtaining high quality bonds over large areas where direct tool pressure is being used to place the titanium sheets into contact with each other. This is due to tolerance build-up in the tools and in the titanium sheets that are used to fabricate the components. Also, because the parts are partially formed before bonding begins, material has been pulled away from the bonding area and the thickness in that location is now less than what the tool was designed for which makes achieving a good quality bond even more challenging. Boeing Commercial Airplanes (BCA) is currently advancing the state of the SPF/DB process in several ways. One of these advances is using a different approach for diffusion bonding. The process includes using stop-off between the sheets and diffusion bonding the pack first and then superplastically forming the stiffening features. This generates a component that is very well bonded in the required locations. However, this process also has its challenges. One of these involves how to apply the stop-off material in the proper location using the most cost effective process. Historically, the application method has been silk screening. A new method has been developed for applying the stop-off that eliminates the need for several pieces of equipment that are required for the silk screening process as well as the associated floor space. Another advancement has been in the development of a different titanium alloy for use in SPF/DB structure.
Authors: Jie Shao, Zhi Qiang Li, Xiu Quan Han, Xiao Ning Han, Ying Deng
Abstract: In this paper, we proposed a new superplastic forming and diffusion bonding (SPF/DB) structure and processed validation between traditional SPF/DB four sheets structure and the new structure at the coincidence boundary conditions by FEM method. The calculation results show that the new structure can decreases the maximum stress at the joining part by 82% and decreases the maximum displacement at the aerofoil tip by 51% at the cost of the mass increases less than 20%. It induces that the new structure presents better stiffness and greater load carrying capacity than traditional ones, therefore, it could be used in titanium main load-carrying structure especially the structure which has the assembling and lose weight requirement very effectively.
Authors: Zhi Qiang Li, He Ping Guo
Abstract: As a versatile fabrication process for titanium and aluminum alloys, SPF/DB offers a real potential for revolutionizing aerospace component design. In this paper, the principle, advantages, techno-economics of the process, as well as its application in aerospace industry are introduced. The current trends and the factors relating to the process’s developments are given.
Authors: Shinichi Yajima, M. Shimanuki, Toshimichi Ogisu, Shigeru Kimura, Hideto Oyama
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