The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Jong-hoon Yoon - One of the best experts on this subject based on the ideXlab platform.
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A study on Diffusion Bonding of steel and copper alloy
Materialwissenschaft Und Werkstofftechnik, 2011Co-Authors: Jong-hoon Yoon, Y.‐m. YiAbstract:In combustion chamber of liquid propellant launch vehicle, the inner shell of the chamber is copper alloy with cooling channels for regenerative cooling and outer shell is steel to maintain high pressure inside the chamber. The purpose of this study is to find the optimum condition for Diffusion Bonding of copper and steel and the experimental conditions were 3 different pressures at temperatures from 800°C to 950°C. In order to characterize the flow strength of materials at high temperatures, several tensile tests were performed at several temperatures from 800°C to 950°C. This information is used to estimate the test condition for Diffusion Bonding and superplastic forming. Mechanical properties of bonded specimen were evaluated with single lap joint tests and shear tests. Microstructure of bonded layer has been also observed with SEM with EDX. It is shown that the optimum condition of Diffusion Bonding is 7 MPa at 890°C, for one hour. Pressurization test of bonded specimen with cooling channels was performed with hydraulic pressure of 87 MPa without failure.
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Manufacturing of Aerospace Parts with Diffusion Bonding Technology
Applied Mechanics and Materials, 2011Co-Authors: Jong-hoon YoonAbstract:The objective of this study is to manufacture aerospace components with Diffusion Bonding technology. Examples produced with this technology consist of thin-sheet Diffusion Bonding and massive Diffusion Bonding. The mechanism of Diffusion Bonding process was presented with schematic microstructure development. Aerospace parts include titanium tanks and a scaled combustion chamber with bonded steel and copper. The microstructure of bonded region shows no indication of heterogeneous phases at interface. It is shown that the Diffusion Bonding of aerospace materials was successfully performed to manufacture lightweight aerospace parts.
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Fabrication of titanium parts by massive Diffusion Bonding
Journal of Materials Processing Technology, 2008Co-Authors: Jong-hoon Yoon, Yeong Moo YiAbstract:Abstract Massive Diffusion Bonding (MDB) is an innovative manufacturing method to produce heavy titanium parts with solid-state Bonding of multi-sheets by applying low pressure of inert gas. Massive solid-state Bonding is different from conventional Diffusion Bonding, which is utilized for sandwich panels during superplastic forming of two or three thin-sheets. The advantages of MDB are its ability to produce heavy titanium sections with less materials waste relative to conventional method such as mechanical machining from solid bulk. It is also possible to produce closed sections, which could not be manufactured by extrusion or forging. In this study massive Diffusion Bonding process of titanium sheets was developed in an inert gas environment. Massive Diffusion Bonding of 40 sheets with thickness of 2 mm was completed in a furnace at 1173 K, pressure of 4 MPa for 1 h in inert gas environment. Using gas pressure as a loading medium prevents Bonding area from the non-uniform pressure application. From pre-sized multi-sheets of titanium, near net shape forming was possible with this process so that significant weight and cost saving was possible.
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Superplastic Characteristics and Diffusion Bonding of Ti-6Al-4V Alloy
Key Engineering Materials, 2007Co-Authors: Jong-hoon Yoon, Yeong Moo Yi, Dong Hyuk ShinAbstract:It is known that Ti-6Al-4V alloy is one of the excellent candidates for aerospace structure due to their high specific strength.However, its higher cost and low formability relative to other materials tend to limit the wide usage of the material.The purpose of this study is to characterize the superplasticity of this alloy so to obtain materials and process parameters for superplastic forming and Diffusion Bonding for industrial application. High temperature tensile tests was carried out at the strain rate range of 10-4 to 10-2 s-1 and temperature range of 1123°C to 1223°C. According to the results of the experiment, the optimum Diffusion Bonding condition was obtained at 1148°C, applying pressure of 4MPa for 1 hour in argon gas environment, which condition is more practical than expensive vacuum condition. It is shown that at the optimum condition for Diffusion Bonding with parent metal, the oxide film becomes unstable and the oxygen is diffused into the bulk. At this condition, the mechanical and microstructural integrity at the Bonding interface was observed in a sandwich structure and a heavy block of titanium part from massive Diffusion Bonding process.
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a study on Diffusion Bonding of superplastic ti 6al 4v eli grade
Journal of Materials Processing Technology, 2007Co-Authors: Jong-hoon Yoon, Chan Hee Park, Young Gun Ko, Dong Hyuk ShinAbstract:Abstract Ti–6Al–4V ELI (extra low interstitials) grade alloy provides improved ductility and fracture toughness comparing to grade 5 Ti–6Al–4V alloy. In order to find the optimum superplastic forming and Diffusion Bonding (SPF/DB) condition, a series of tensile tests was carried out at the strain rate range of 10 −4 to 10 −2 s −1 and temperature range of 1073–1223 K. The maximum elongation of 1898% was obtained at the strain rate of 10 −3 s −1 at 850 °C. It was shown that the ELI grade alloy performs better than the grade 5 alloy in terms of the optimum superplastic condition for Ti–6Al–4V. Based on this result, Diffusion Bonding process of superplastic Ti–6Al–4V ELI sheet metals was developed. Bonding was completed by means of inert gas pressure applied in a Bonding tool at high temperature. The microstructure of the Bonding area was investigated and the Bonding interface was microscopically undetectable. The evidence of nucleation of new grains and migration of grain boundaries at the interface proves the Diffusion Bonding process is successful. It is shown that the superplastic forming and Diffusion Bonding of Ti–6Al–4V ELI grade is possible at the temperature lower than those of conventional Ti–6Al–4V.
He Fang - One of the best experts on this subject based on the ideXlab platform.
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superplastic forming and Diffusion Bonding of ti 22al 24nb alloy
Journal of Materials Processing Technology, 2015Co-Authors: Changwen Wang, Tao Zhao, Guofeng Wang, He FangAbstract:Abstract In order to analyze superplasticity and Diffusion Bonding of Ti–22Al–24Nb, uniaxial tensile experiment at high temperature, vacuum Diffusion Bonding and superplastic forming were carried out based on Ti–22Al–24Nb alloy. The results show that Ti–22Al–24Nb has the best superplasticity under temperature of 960 °C and strain rate of 0.0005 s−1; by observing the Diffusion Bonding interface by metallographic microscope and conducting shear strength tests, it finds that under temperature of 960 °C and holding time of 2 h, with the increase of pressure within certain limit, effect of Diffusion Bonding gets better; after superplastic forming, the box-shaped component fits the die well, wall thickness is well distributed in general, and it has enough tensile strength at room temperature and high temperature.
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Superplastic forming and Diffusion Bonding of Ti–22Al–24Nb alloy
Journal of Materials Processing Technology, 2015Co-Authors: Changwen Wang, Tao Zhao, Guofeng Wang, He FangAbstract:Abstract In order to analyze superplasticity and Diffusion Bonding of Ti–22Al–24Nb, uniaxial tensile experiment at high temperature, vacuum Diffusion Bonding and superplastic forming were carried out based on Ti–22Al–24Nb alloy. The results show that Ti–22Al–24Nb has the best superplasticity under temperature of 960 °C and strain rate of 0.0005 s−1; by observing the Diffusion Bonding interface by metallographic microscope and conducting shear strength tests, it finds that under temperature of 960 °C and holding time of 2 h, with the increase of pressure within certain limit, effect of Diffusion Bonding gets better; after superplastic forming, the box-shaped component fits the die well, wall thickness is well distributed in general, and it has enough tensile strength at room temperature and high temperature.
Dong Hyuk Shin - One of the best experts on this subject based on the ideXlab platform.
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Superplastic Characteristics and Diffusion Bonding of Ti-6Al-4V Alloy
Key Engineering Materials, 2007Co-Authors: Jong-hoon Yoon, Yeong Moo Yi, Dong Hyuk ShinAbstract:It is known that Ti-6Al-4V alloy is one of the excellent candidates for aerospace structure due to their high specific strength.However, its higher cost and low formability relative to other materials tend to limit the wide usage of the material.The purpose of this study is to characterize the superplasticity of this alloy so to obtain materials and process parameters for superplastic forming and Diffusion Bonding for industrial application. High temperature tensile tests was carried out at the strain rate range of 10-4 to 10-2 s-1 and temperature range of 1123°C to 1223°C. According to the results of the experiment, the optimum Diffusion Bonding condition was obtained at 1148°C, applying pressure of 4MPa for 1 hour in argon gas environment, which condition is more practical than expensive vacuum condition. It is shown that at the optimum condition for Diffusion Bonding with parent metal, the oxide film becomes unstable and the oxygen is diffused into the bulk. At this condition, the mechanical and microstructural integrity at the Bonding interface was observed in a sandwich structure and a heavy block of titanium part from massive Diffusion Bonding process.
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a study on Diffusion Bonding of superplastic ti 6al 4v eli grade
Journal of Materials Processing Technology, 2007Co-Authors: Jong-hoon Yoon, Chan Hee Park, Young Gun Ko, Dong Hyuk ShinAbstract:Abstract Ti–6Al–4V ELI (extra low interstitials) grade alloy provides improved ductility and fracture toughness comparing to grade 5 Ti–6Al–4V alloy. In order to find the optimum superplastic forming and Diffusion Bonding (SPF/DB) condition, a series of tensile tests was carried out at the strain rate range of 10 −4 to 10 −2 s −1 and temperature range of 1073–1223 K. The maximum elongation of 1898% was obtained at the strain rate of 10 −3 s −1 at 850 °C. It was shown that the ELI grade alloy performs better than the grade 5 alloy in terms of the optimum superplastic condition for Ti–6Al–4V. Based on this result, Diffusion Bonding process of superplastic Ti–6Al–4V ELI sheet metals was developed. Bonding was completed by means of inert gas pressure applied in a Bonding tool at high temperature. The microstructure of the Bonding area was investigated and the Bonding interface was microscopically undetectable. The evidence of nucleation of new grains and migration of grain boundaries at the interface proves the Diffusion Bonding process is successful. It is shown that the superplastic forming and Diffusion Bonding of Ti–6Al–4V ELI grade is possible at the temperature lower than those of conventional Ti–6Al–4V.
E. R. Wallach - One of the best experts on this subject based on the ideXlab platform.
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Diffusion Bonding: development of theoretical model
Metal science, 2013Co-Authors: Brian Derby, E. R. WallachAbstract:AbstractIn previous work, a theoretical model for solid state Diffusion Bonding was described. Possible Diffusion Bonding mechanisms were identified and mass transport rate equations for each proposed in terms of both process variables (time, temperature, pressure) and material properties. However, the mechanism of mass transfer in the vapour phase was not described since, for many Diffusion Bonding applications, the contribution from this mechanism will not be significant. For completeness, the vapour phase mass transport rate equations now are derived. In addition, a revised model is presented for the power law creep mechanism, based on considerations of the elastic and plastic deformation of a long triangular ridge. This new approach eliminates the assumptions, implicit in the earlier work, which break down in the later stages of Diffusion Bonding when the interface is substantially bonded; better agreement with experimental data also is obtained.
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Theoretical model for Diffusion Bonding
Metal science, 2013Co-Authors: Brian Derby, E. R. WallachAbstract:AbstractDespite successful applications of Diffusion Bonding, there is uncertainty as to the dominant mechanisms which operate when the two surfaces to be joined are brought together under an applied pressure at an elevated temperature. This paper describes a theoretical model for solid-state Diffusion Bonding, the aim of which is to understand how the various competing mechanisms operating at the bond interface are affected both by process variables (time, temperature, pressure) and by the properties of the materials being joined. Thus in the model the rate-controlling mechanisms governing the elimination of the interface between the two surfaces are identified, their relative kinetics predicted, and their individual importance in the various stages of Diffusion Bonding assessed. The approach adopted bears some similarity with that used when modelling the pressure sintering of powders, although the geometry at the interface of a Diffusion bond results in differences.
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interface evolution and bond strength when Diffusion Bonding materials with stable oxide films
Surface and Interface Analysis, 2001Co-Authors: A A Shirzadi, H Assadi, E. R. WallachAbstract:The effects of stable surface oxides on the interface morphologies and strengths of aluminium Diffusion bonds are reviewed. Previous approaches, proposed to overcome problems with surface oxides when joining aluminium alloys and composites, are described and compared for both solid-state Diffusion Bonding and conventional transient liquid-phase Diffusion Bonding. Non-conventional joining methods, particularly the new method of temperature-gradient transient liquid-phase Diffusion Bonding and its capability of producing high-strength bonds reliably, also are considered. Copyright © 2001 John Wiley & Sons, Ltd.
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Diffusion Bonding of tial
Intermetallics, 1993Co-Authors: E. R. WallachAbstract:Abstract Diffusion-Bonding of TiAl (48 at.% Al) using both solid-state and transient-liquid-phase (TLP) processes was studied. In solid-state Diffusion-Bonding, dynamic recrystallization which occurs at the bond-line during Bonding is found to have a significant effect on improving bond strength. The use of interlayers in the solid-state process makes it possible to fabricate bonds at a comparatively low Bonding temperature and pressure, and to produce bonds having overall properties compatible with the base material after Diffusion of interlayers using post-bond heat treatments. In the TLP process, the Bonding temperature, which is determined by the melting temperature of the filler alloys, controls Diffusion and any interaction between the base material and filler alloy. Ternary inter-metallic phases may form when using low-melting-temperature filler alloys but were not found when using high-melting-temperature filler alloys. The high-melting filler alloys can be used confidently to produce TLP bonds with good mechanical properties. Post-bond heat treatments are found to change microstructural constituent ratios and to affect properties of both the base material and TiAl joints, especially when interlayers or filler alloys are used. The beneficial effect of interlayer or filler alloy elements on bond properties through post-bond heat treatments is remarkable, resulting in the overall properties of bond regions being better than those of the base material.
Changwen Wang - One of the best experts on this subject based on the ideXlab platform.
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superplastic forming and Diffusion Bonding of ti 22al 24nb alloy
Journal of Materials Processing Technology, 2015Co-Authors: Changwen Wang, Tao Zhao, Guofeng Wang, He FangAbstract:Abstract In order to analyze superplasticity and Diffusion Bonding of Ti–22Al–24Nb, uniaxial tensile experiment at high temperature, vacuum Diffusion Bonding and superplastic forming were carried out based on Ti–22Al–24Nb alloy. The results show that Ti–22Al–24Nb has the best superplasticity under temperature of 960 °C and strain rate of 0.0005 s−1; by observing the Diffusion Bonding interface by metallographic microscope and conducting shear strength tests, it finds that under temperature of 960 °C and holding time of 2 h, with the increase of pressure within certain limit, effect of Diffusion Bonding gets better; after superplastic forming, the box-shaped component fits the die well, wall thickness is well distributed in general, and it has enough tensile strength at room temperature and high temperature.
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Superplastic forming and Diffusion Bonding of Ti–22Al–24Nb alloy
Journal of Materials Processing Technology, 2015Co-Authors: Changwen Wang, Tao Zhao, Guofeng Wang, He FangAbstract:Abstract In order to analyze superplasticity and Diffusion Bonding of Ti–22Al–24Nb, uniaxial tensile experiment at high temperature, vacuum Diffusion Bonding and superplastic forming were carried out based on Ti–22Al–24Nb alloy. The results show that Ti–22Al–24Nb has the best superplasticity under temperature of 960 °C and strain rate of 0.0005 s−1; by observing the Diffusion Bonding interface by metallographic microscope and conducting shear strength tests, it finds that under temperature of 960 °C and holding time of 2 h, with the increase of pressure within certain limit, effect of Diffusion Bonding gets better; after superplastic forming, the box-shaped component fits the die well, wall thickness is well distributed in general, and it has enough tensile strength at room temperature and high temperature.