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Manufacturing Techniques
Published in Sumit Sharma, Composite Materials, 2021
Diffusion bonding is a common solid-state welding technique used to join similar or dissimilar metals. Interdiffusion of atoms from clean metal surfaces in contact at an elevated temperature leads to welding. There are many variants of the basic diffusion bonding process; however, all of them involve a step of simultaneous application of pressure and high temperature. Matrix alloy foil and fiber arrays, composite wire, or monolayer laminae are stacked in a predetermined order. Figure 3.20 shows a schematic of one such diffusion bonding process, also called the foil-fiber-foil process. Vacuum hot pressing is a most important step in the diffusion bonding processes for MMCs. The major advantages of this technique are the ability to process a wide variety of matrix metals and control of fiber orientation and volume fraction. The disadvantages are processing times of several hours, and high processing temperatures and pressures – all of which make the process quite expensive – besides the fact only objects of limited size can be produced. Hot isostatic pressing (HIP), instead of uniaxial pressing, can also be used. In HIP, gas pressure against a can consolidates the composite piece contained inside the can. With HIP, it is relatively easy to apply high pressures at elevated temperatures over variable geometries.
Diffusion Bonding
Published in Yoseph Bar-Cohen, Advances in Manufacturing and Processing of Materials and Structures, 2018
Diffusion bonding is a process of joining two similar or dissimilar materials through facilitating an interface cross-diffusion of elemental species at elevated temperature and pressure, hence forming a permanent bond of mating surfaces. The formal definition of this process suggested is “Diffusion bonding of materials in the solid state is a process for making a monolithic joint through the formation of bonds at atomic level, as a result of closure of the mating surfaces due to the local plastic deformation at elevated temperature which aids interdiffusion at the surface layers of the materials being joined” (Kazakov, 2013). This definition follows the formulation proposed in late 1980s of the last century. In general, there are two main variants of diffusion bonding for material joining (metal–metal, metal–nonmetal, or nonmetal–nonmetal): (i) solid-state diffusion bonding and (ii) transient liquid phase (TLP) diffusion bonding (Loh and Wu, 1993; Zhou, 2004). Solid-state diffusion bonding is the classical diffusion bonding process, which involves only the solid state during the whole process (i.e., no material melting takes place), while liquid phase transient diffusion bonding is the combination of classical diffusion bonding (before the liquid phase occurs) and isothermal brazing (after the liquid phase occurs) (Zhou, 2004). During TLP diffusion bonding, a liquid layer is formed during the bonding process at the interface and then, as a consequence of a continued interdiffusion at the bonding temperature and imposed pressure, an isothermal solidification occurs to facilitate the formation of the bond (Loh and Wu, 1993). The difference between TLP diffusion bonding and brazing is that the solidification of the liquid phase in TLP is in the isothermal phase, while brazing is often in the cooling phase.
Joining of Metals
Published in Sherif D. El Wakil, Processes and Design for Manufacturing, 2019
Diffusion bonding is a solid-state welding method in which the surfaces to be welded are cleaned and then maintained at elevated temperatures under appropriate pressure for a long period of time. No fusion occurs, deformation is limited, and bonding takes place principally due to diffusion. As we know from metallurgy, the process parameters are pressure, temperature, and time, and they should be adjusted to achieve the desired results.
Analysis and Preliminary Design of Primary Heat Exchanger Failure Testing Facility for Lead-Cooled Fast Reactors
Published in Nuclear Technology, 2023
Federico Hattab, Fabio Giannetti, Vincenzo Narcisi, Pierdomenico Lorusso, Filippo Bussoletti, Michael Epstein, Sung Jin Lee, Mariano Tarantino
In nuclear reactor systems, the PCHE could be as important as a “safety-related” component due to its boundary function of the reactor coolant system, and its design reference construction code is the ASME Boiler and Pressure Vessel Code, Sec. III (Ref. 18). Three variables play an important role in the diffusion bonding process: the bonding temperature, the bonding pressure, and the holding time.19 The bonding temperature and pressure should be adequately lower than the parent metal absolute melting point and the material yield strength, respectively.20 Because of the high temperature and pressure differentials anticipated in the proposed nuclear applications, careful design is required in order to ensure that internal stresses do not cause flow passage deformation and/or failure.21
Additive manufacturing of bimetallic structures
Published in Virtual and Physical Prototyping, 2022
Amit Bandyopadhyay, Yanning Zhang, Bonny Onuike
A bimetallic structure could be processed using conventional or additive manufacturing (AM) methods, as shown in Figure 2. Welding and brazing techniques are probably the most commonly used conventional methods for joining two different metallic materials. Different welding techniques such as arc welding, explosion welding, laser butt welding, and friction stir welding can be applied for joining (Nandan, DebRoy, and Bhadeshia 2008; Rai et al. 2011; Mishra et al. 2008; Velu and Bhat 2015; Fallahi et al. 2017; Casalino et al. 2017; Liu, Jia, and Xuan 2017; Zu, Sun, and Zhang 2017; Ning et al. 2017). Although welding techniques to join two metallic materials is economical, there are still some critical issues for bimetallic structures, such as leading a sizeable heat-affected zone (HAZ) at the joint and cracking due to brittle intermetallic phase formation, especially for joining two dissimilar metals. Brazing, a liquid–solid-state bonding process, is performed at a lower temperature than welding. This process is used with filler (braze) metal to join wide varieties of dissimilar metals with improved bonding strength. Diffusion bonding is increasingly used to join difficult-to-bond combinations of materials, such as immiscible dissimilar metals, metals to ceramics combinations, by applying pressure and heat at joining surfaces where the strength of the diffusion-bonded joint is a function of plastic deformation.
Fabrication of copper/stainless steel bimetallic couple, by diffusion bonding using silver and nickel foils as interlayers
Published in Inorganic and Nano-Metal Chemistry, 2019
Mansoor Ekrami, Javad Shahbazi Karami, Alireza Araee, Fariborz Sharifianjazi, Ehsan Sadeghi, Amirhossein Moghanian
Diffusion bonding technique of joining materials produces qualified joints without considerable shape deformation and the need for finishing machining.[33] The higher quality in bonding area can be acquired by appending a filler material as an interlayer between two joining materials.[34,35] Diffusion bonding is used to join both similar and dissimilar materials which can present a bond with mechanical properties close to base metals and bonding interfaces with minimum cracks and voids and approximately no phase transformation or change in microstructure.[34–37] The mechanical properties and microstructure of bonding area are controlled by major parameters such as temperature, pressure and holding time in addition use of interlayer. In previous studies, Nickel and Silver have been used as interlayer in diffusion bonding of stainless steel and copper to other materials.[38] For joining of stainless steel (AISI 316) to copper when it diffusion bonded without interlayer, many micro-voids was propagated at Cu side in grain boundaries due to different inherent diffusion coefficients of two material that were joined.[30] Nishi et al. exerted Au, Cu and Ni foil to avoid intermetallic compound. The results demonstrated the joint with a Ni interlayer at the bond area with less elongation than that of Cu and microvoids were formed at Cu side of interface.[17] In diffusion bonding of oxygen-free Cu to TC4 by application of silver interlayer, the joint showed increase in tensile strength and a solid solution without intermetallic composite formed in Ag/OFC interface[38] also in another work silver used as interlayer in SS (grade 304) to titanium alloy to prevent creation of intermetallic phases in diffusion zone.[38,39] Few researchers have benefited from two interlayer composite[32] to decrease bonding temperature to facilitate industrial manufacturing bonded joints and avoid of microstructural changes and deformation.