Special Issue "Advanced Tungsten Materials"

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

Deadline for manuscript submissions: closed (30 June 2019).

Special Issue Editor

Guest Editor
Dr. Jan Willem Coenen Website E-Mail
Forschungszentrum Julich, Institute of Energy & Climate Research, Julich, Germany
Interests: Nuclear Fusion; Plasma Material Interaction; Tungsten; Refractory Metal Composites; Tungsten-Fibre Reinforced Tungsten; Material Science; Sintering

Special Issue Information

Dear Colleagues,

Tungsten (W) is the metal for extreme environments as it has the highest melting point However, tungsten has two main disadvantages: poor oxidation resistance at temperatures above 600 °C as well as a low room temperature (RT) fracture toughness, KIQ, and a brittle-to-ductile transition (BDT) that occurs at high temperatures. This is why tungsten is currently only used as a functional material and not as a structural material, that is, not for safety relevant, pressurized parts. Consequently, thinking about tungsten as a structural material, the question of how to make tungsten ductile and how to decrease the brittle-to-ductile transition temperature (BDTT) arises.

The purpose of this special issue is thus to compile the current status of work related to the improvement of the properties of tungsten for applications such as fusion, and other extreme environments, e.g. solar thermal power.

Contributions related to the manufacture of new tungsten materials, studies of W-composites, their constituent components as well as modelling and material characterization methods will be accepted.

Dr. Jan Willem Coenen
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 1500 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

  • Tungsten
  • Composites
  • MMC
  • Alloys, Fibres
  • Laminates
  • Nuclear Fusion
  • Advanced Materials

Published Papers (3 papers)

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Research

Open AccessArticle
On the Structural and Chemical Homogeneity of Spark Plasma Sintered Tungsten
Metals 2019, 9(8), 879; https://doi.org/10.3390/met9080879 - 10 Aug 2019
Abstract
Tungsten-based materials are the prime candidate plasma-facing materials for future fusion reactors, such as DEMO. Spark plasma sintering is a prospective fabrication technology with several advantageous features. The concurrent application of electric current, temperature and pressure enhances the sintering process, allowing for lower [...] Read more.
Tungsten-based materials are the prime candidate plasma-facing materials for future fusion reactors, such as DEMO. Spark plasma sintering is a prospective fabrication technology with several advantageous features. The concurrent application of electric current, temperature and pressure enhances the sintering process, allowing for lower temperatures and shorter sintering times than traditional powder metallurgy processes. This in turn helps to avoid excessive grain growth and phase segregation in W-alloys. This study is focused on several factors that may influence the homogeneity of the sintered compacts—namely the diffusion of carbon from the graphite die, purity of the powder and sintering conditions. The following characteristics of spark plasma-sintered tungsten compacts were studied: composition (especially carbon and oxygen content), porosity, mechanical properties (hardness and fracture strength), and thermal diffusivity. The effects of the abovementioned processing factors were quantified, and local variations of selected properties were assessed. Full article
(This article belongs to the Special Issue Advanced Tungsten Materials)
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Open AccessArticle
Mechanical Properties and Microstructure of W-6Ni-4Co Alloy by a Two-Step Sintering Process
Metals 2019, 9(6), 680; https://doi.org/10.3390/met9060680 - 13 Jun 2019
Abstract
The mechanical properties and microstructure of W-6Ni-4Co alloy through solid phase sintering and two-step sintering process were investigated. The results demonstrated that the particle sizes of W-6Ni-4Co alloy milled powders increased firstly and decreased later during a mechanical alloying process. The shape of [...] Read more.
The mechanical properties and microstructure of W-6Ni-4Co alloy through solid phase sintering and two-step sintering process were investigated. The results demonstrated that the particle sizes of W-6Ni-4Co alloy milled powders increased firstly and decreased later during a mechanical alloying process. The shape of alloy milled powders affected that of grains in alloy by solid phase sintering. The shape of W-rich particles in the alloys changed from stripes to network, to polygonal and to subsphaeroidal finally during two-step sintering process. The mechanical properties could be attributed to the densification and microstructure of alloys, and increased during two-step sintering with short dwelling time. Full article
(This article belongs to the Special Issue Advanced Tungsten Materials)
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Open AccessArticle
Electronic Structure Calculations of Oxygen Atom Transport Energetics in the Presence of Screw Dislocations in Tungsten
Metals 2019, 9(2), 252; https://doi.org/10.3390/met9020252 - 20 Feb 2019
Abstract
Plastic flow in body-centered cubic (bcc) alloys is governed by the thermally-activated motion of screw dislocations in close-packed planes. In bcc interstitial solid solutions, solute diffusion can occur at very fast rates owing to low migration energies and solute concentrations. Under mechanical loading, [...] Read more.
Plastic flow in body-centered cubic (bcc) alloys is governed by the thermally-activated motion of screw dislocations in close-packed planes. In bcc interstitial solid solutions, solute diffusion can occur at very fast rates owing to low migration energies and solute concentrations. Under mechanical loading, solutes may move on the same or similar time scale as dislocations glide, even at low temperatures, potentially resulting in very rich co-evolution processes that may have important effects in the overall material response. It is therefore important to accurately quantify the coupling between interstitial impurities and dislocations, so that larger-scale models can correctly account for their interactions. In this paper, we use electronic structure calculations to obtain the energetics of oxygen diffusion under stress and its interaction energy with screw dislocation cores in bcc tungsten. We find that oxygen atoms preferentially migrate from tetrahedral to tetrahedral site with an energy of 0.2 eV. This energy couples only weakly to hydrostatic and deviatoric deformations, with activation volumes of less than 0.02 and 0.02 b 3 , respectively. The strongest effect is found for the inelastic interaction between O atoms and screw dislocation cores, which leads to attractive energies between 1.2 and 1.9 eV and sometimes triggers a transformation of the screw dislocation core from an easy core configuration to a hard core configuration. Full article
(This article belongs to the Special Issue Advanced Tungsten Materials)
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