Special Issue "Diffusion Bonding of Metals"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: 29 February 2020.

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 papers will be 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 1600 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 (3 papers)

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Research

Open AccessArticle
Optimization of Copper Thermocompression Diffusion Bonding under Vacuum: Microstructural and Mechanical Characteristics
Metals 2019, 9(10), 1044; https://doi.org/10.3390/met9101044 - 26 Sep 2019
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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Open AccessArticle
Enhancing the Mechanical Properties of Hot Roll Bonded Al/Ti Laminated Metal Composites (LMCs) by Pre-Rolling Diffusion Process
Metals 2019, 9(7), 795; https://doi.org/10.3390/met9070795 - 18 Jul 2019
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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Open AccessArticle
Microstructures and Mechanical Properties of Mg-9Al/Ti Metallurgical Bonding Prepared by Liquid-Solid Diffusion Couples
Metals 2018, 8(10), 778; https://doi.org/10.3390/met8100778 - 29 Sep 2018
Cited by 2
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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