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Metals
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Diffusion Bonding of Metals
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Diffusion Bonding of Metals

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metal Casting, Forming and Heat Treatment".

Deadline for manuscript submissions: closed (29 February 2020) | Viewed by 14959

Special Issue Editor

Dr. Thomas Gietzelt

E-Mail Website
Guest Editor
Institute for Micro Process Engineering, Karlsruhe Institute of Technology, PoBox 3640, 76021 Karlsruhe, Germany
Interests: joining technologies, diffusion bonding, laser welding, materials technology, materials diagnostics; application of new materials; corrosion phenomena

Special Issue Information

Dear Colleagues,

Diffusion bonding is an amazing technology for producing holohedral joints, and also of internal structures. Although expensive equipment is required to maintain an inert atmosphere at high temperatures, and an external load has to be applied to the parts to be joined, diffusion bonding is used extensively in, e.g., aerospace industries and for internal cooling structures for molding tools.

The main process parameters are bonding temperature, dwell time, and bearing pressure. In addition, the aspect ratio and the number of layers to be bonded affect deformation during the diffusion bonding process.

Furthermore, additional issues must be considered to reach the goal, forming a monolithic part with vacuum tightness and resistance to high internal pressures by grain growth across bonding planes. For this, surface roughness must be leveled. Apart from the roughness values affecting vacuum tightness, the number of layers has an impact on the degree of deformation.

Materials science aspects resulting from the heat treatment, such as grain growth and its impact on mechanical or corrosive properties of the materials, must be considered.

To facilitate grain growth across bonding planes, the passivation layer must be soluble in the bulk material or must be removed by appropriate surface preparation, e.g. by brushing or pickling.

Interlayers like thin amorphous foils or additional metals deposited by PVD-processes may facilitate bonding by formation of a temporary liquid phase due to high interfacial energy or forming eutectic compositions. The occurrence of liquid phases at considerably lower temperature helps to limit grain growth of the matrix material, and the coefficient of diffusion in liquids is several orders of magnitude higher than in solids.

For this Special Issue in Metals, we welcome research articles and reviews addressing theoretical aspects, specific designs for diffusion bonding, diffusion bonding equipment, surface preparation, bonding experiments of all kinds of metallic materials, including use of different inter- and multilayers, preparation and characterization of diffusion-bonded parts, as well as examples of applications of diffusion bonding.

Dr. Thomas Gietzelt
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Diffusion bonding
  • Diffusion welding
  • Temporary liquid phase (TLP)
  • Amorphous interlayer
  • Surface pretreatment
  • Passivation layer
  • Deformation
  • Microstructure
  • Aspect ratio
  • Micro process engineering

Published Papers (5 papers)

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Research

17 pages, 21215 KiB  
Article
Comprehensive Study of the Deformation Behavior during Diffusion Bonding of 1.4301 (AISI 304) as a Function of Material Width and Aspect Ratio
by Thomas Gietzelt, Volker Toth, Manfred Kraut, Uta Gerhards and Robin Dürrschnabel
Metals 2020, 10(9), 1116; https://doi.org/10.3390/met10091116 - 19 Aug 2020
Viewed by 1986
Abstract
In this paper, the impact of material width as well as aspect ratio on deformation during diffusion bonding of layered samples were investigated. For this, six annular samples with a constant cross-sectional area but an increasing diameter and thus decreasing material width were [...] Read more.
In this paper, the impact of material width as well as aspect ratio on deformation during diffusion bonding of layered samples were investigated. For this, six annular samples with a constant cross-sectional area but an increasing diameter and thus decreasing material width were designed. In a first set of experiments, specimens of a constant height of h = 20 mm were examined. Each sample consisted of 10 sheets, 2 mm in thickness each. Diffusion bonding was performed at T = 1075 °C, t = 4 h and p = 15 MPa. Subsequently, additional samples with a constant aspect ratio of about three but different material width were diffusion bonded. For this, additional layers were added. It was expected that the deformation should be nearly constant for a constant aspect ratio. However, comparing the deformation to a sample possessing an aspect ratio of about three from the first batch, a much higher deformation was obtained now. Bonding a third sample, a deformation in the same range as for the other two samples of the second batch was obtained. It was found that due to the evaporation of metals, the thermocouples were subjected to aging, which was proven indirectly by the evaluation of heating power. Since the diffusion coefficient of the metals follows an exponential law, deformation changes considerably with temperature. This emphasizes that exact temperature measurement is very important, especially for bonding microprocessor devices at constant contact pressure. The experiments showed that the deformation depends strongly on geometry. Bonding parameters cannot be generalized. For layered setups, the contribution that thickness tolerances from manufacturing and leveling of surface roughnesses of sheets add to the overall deformation cannot be reliably separated. After diffusion bonding, thickness tolerances increase with a lateral dimension. Obviously, the stiffness of the pressure dies is crucial. Full article
(This article belongs to the Special Issue Diffusion Bonding of Metals)
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18 pages, 8470 KiB  
Article
Highly Molybdenum-Alloyed Materials Hastelloy BC-1 (2.4708) and B3 (2.4600): Diffusion Bonding Experiments and Evaluation of both Mechanical Behavior and Corrosion Resistance in Hot 70% Sulfuric Acid
by Thomas Gietzelt, Mario Walter, Volker Toth, Florian Messerschmidt and Ralf Dahm
Metals 2020, 10(3), 376; https://doi.org/10.3390/met10030376 - 14 Mar 2020
Cited by 2 | Viewed by 3026
Abstract
Sulfuric acid is a widely used raw material in the chemical industry. Its corrosive effect on materials varies considerably, depending on impurities, temperature and water content. This is an issue for micro process apparatuses with thin walls. Such devices are often joint by [...] Read more.
Sulfuric acid is a widely used raw material in the chemical industry. Its corrosive effect on materials varies considerably, depending on impurities, temperature and water content. This is an issue for micro process apparatuses with thin walls. Such devices are often joint by diffusion bonding what may alter materials properties due to high temperatures and long dwell times. In this paper, two high molybdenum alloys, namely Hastelloy B3 and BC-1, were investigated. Diffusion bonding tests were performed at different temperatures. Tensile tests were carried out for different material conditions, to determine the change in mechanical strength and elongation at fracture values. The fracture behavior of both alloys was ductile and the fracture surfaces showed dimple structure. For diffusion bonded samples, weak spots or rather non-bonded areas were found. These obviously caused the onset of material failure and thus, degradation of mechanical properties. Tensile samples, aged in 70% sulfuric acid at 100 °C for 1000 h showed local corrosion attacks at the grain boundaries at the circumferential surfaces and joining planes—for Hastelloy B3 more pronounced than for Hastelloy BC-1. Accordingly, a further decrease of stress and elongation at fracture values was observed. However, 0.2% yield strength used for dimensioning components are found to be reasonable. As conclusion, at least Hastelloy BC-1 reveals both good mechanical properties and an excellent corrosion resistance, regardless of the heat treatment. This is a significant advance compared to the results obtained from a previously research project on four different alloys. Full article
(This article belongs to the Special Issue Diffusion Bonding of Metals)
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10 pages, 5091 KiB  
Article
Optimization of Copper Thermocompression Diffusion Bonding under Vacuum: Microstructural and Mechanical Characteristics
by Michail Samouhos, Antonis Peppas, Panagiotis Angelopoulos, Maria Taxiarchou and Petros Tsakiridis
Metals 2019, 9(10), 1044; https://doi.org/10.3390/met9101044 - 26 Sep 2019
Cited by 5 | Viewed by 2849
Abstract
The optimization of the autogenous diffusion copper bonding via thermocompression at vacuum environment was investigated. The influence of various bonding parameters on the interdiffusion efficiency was studied in detail at the micro (SEM-EBSD) and nano (TEM) scales. Bonding at 1000 °C for 90 [...] Read more.
The optimization of the autogenous diffusion copper bonding via thermocompression at vacuum environment was investigated. The influence of various bonding parameters on the interdiffusion efficiency was studied in detail at the micro (SEM-EBSD) and nano (TEM) scales. Bonding at 1000 °C for 90 min under pressure (10 MPa) presented optimum structural and mechanical results. Under these conditions, interdiffusion phenomena were observed at a significant extent through the swelling transformation of existing fine grains or the formation of equiaxed copper grains with an orientation parallel to the bond interface. Transmission electron microscopy revealed the importance of the grain size of the base material on the bond quality. In the regions with fine-sized copper grains, the formation of small equiaxed recrystallized twins was observed. Their length within the bonding zone was in the order of 200 and 400 nm. On the contrary, in the regions with coarse grains the interdiffusion was poorer. The processing temperature and duration presented a significant effect on the bonding strength (BS). BS exceeded 100 MPa in case of processing conditions of T ≥ 850 °C and t ≥ 60 min, while the maximum BS value achieved (≈180 MPa) was comparable with the respective value of the base material. The microhardness of the optimum bond reached 55 HV—slightly higher in comparison to the hardness of the initial copper material. The results indicated that the proposed thermocompression process is appropriate for the production of Cu-Cu bonded structures that can be potentially used as electrical components under mechanical stress. Full article
(This article belongs to the Special Issue Diffusion Bonding of Metals)
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13 pages, 5936 KiB  
Article
Enhancing the Mechanical Properties of Hot Roll Bonded Al/Ti Laminated Metal Composites (LMCs) by Pre-Rolling Diffusion Process
by Cheng Zhang, Shouxin Wang, Hanxue Qiao, Zejun Chen, Taiqian Mo and Qing Liu
Metals 2019, 9(7), 795; https://doi.org/10.3390/met9070795 - 18 Jul 2019
Cited by 14 | Viewed by 3124
Abstract
In this study, the traditional hot rolling to fabricate Al/Ti laminated metal composites (LMCs) was improved by using a pre-rolling diffusion process. The effect of the pre-rolling diffusion on microstructure and mechanical properties of Al/Ti LMCs were investigated by various methods, such as [...] Read more.
In this study, the traditional hot rolling to fabricate Al/Ti laminated metal composites (LMCs) was improved by using a pre-rolling diffusion process. The effect of the pre-rolling diffusion on microstructure and mechanical properties of Al/Ti LMCs were investigated by various methods, such as optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and tensile tests. The results show that, with increasing diffusion temperature, the thickness in diffusion layer was increased and the mechanical properties of LMCs were improved obviously, which was attributed to the optimized interfacial structure after diffusion process. In addition, the formation of TiAl3 intermetallic compounds (IMCs) was detected in the bonding interface, which played an important role in improving the mechanical properties for Al/Ti LMCs. The predicted results of stress-strain curves from rule of mixture (ROM) indicated that, there existed an extra interfacial strengthening in Al/Ti LMCs beside the mechanical properties provided by the contribution of constituent layers. The pre-rolling diffusion process is effective for the optimization of interfacial structure and improvement of mechanical properties in Al/Ti LMCs. Full article
(This article belongs to the Special Issue Diffusion Bonding of Metals)
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13 pages, 6193 KiB  
Article
Microstructures and Mechanical Properties of Mg-9Al/Ti Metallurgical Bonding Prepared by Liquid-Solid Diffusion Couples
by Jiahong Dai, Bin Jiang, Qiong Yan, Hongmei Xie, Zhongtao Jiang, Qingshan Yang, Qiaowang Chen, Cheng Peng and Fusheng Pan
Metals 2018, 8(10), 778; https://doi.org/10.3390/met8100778 - 29 Sep 2018
Cited by 5 | Viewed by 2884
Abstract
Microstructures and mechanical properties of Mg-9Al/Ti metallurgical bonding prepared by liquid-solid diffusion couples were investigated. The results indicate that a metallurgical bonding was formed at the interface Mg-9Al/Ti, and the Mg17Al12 phase growth coarsening at the interfaces with the increase [...] Read more.
Microstructures and mechanical properties of Mg-9Al/Ti metallurgical bonding prepared by liquid-solid diffusion couples were investigated. The results indicate that a metallurgical bonding was formed at the interface Mg-9Al/Ti, and the Mg17Al12 phase growth coarsening at the interfaces with the increase in heat treatment time. Push-out testing was used to investigate the shear strength of the Mg-9Al/Ti metallurgical bonding. It is shown that the shear strength presents an increasing tendency with the increased heat treatment time. The sequence is characterized, and the results show that the fracture takes place along the Mg-9Al matrix at the interface. The diffusion of Al and Ti elements play a dominant role in the interface reaction of Mg-9Al/Ti metallurgical bonding. By energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and thermodynamic analysis, it was found that Al3Ti is the only intermetallic compound at the interface of Mg-9Al/Ti metallurgical bonding. These results clearly show that chemical interaction at the interface formation of Al3Ti improves the mechanical properties of Mg-9Al/Ti metallurgical bonding. Full article
(This article belongs to the Special Issue Diffusion Bonding of Metals)
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