Special Issue "Thermodynamic Properties, Structure and Phase Stabilities of Special Alloys"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Structure Analysis and Characterization".

Deadline for manuscript submissions: 30 June 2020.

Special Issue Editor

Ass. Prof. Dr. Erwin Povoden-Karadeniz
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Guest Editor
Christian Doppler Laboratory for Interfaces and Precipitation Engineering, Institute of Materials Science and Technology, TU Wien, Getreidemarkt 9, 1060, Vienna, Austria
Interests: metastable phases; special alloy systems; intermetallics; precipitates evolution; functional materials; heterogeneous systems
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Special Issue Information

Dear Colleagues,

The fulfilment of present-day requirements of our consumer society depends on the development of innovative materials to be used in transportation, energy, and communication technology, among various other fields. Moreover, the responsibility for a worth-living environment for the future generations needs to be accepted by implementing sustainable and gentle processes. This can be achieved by the smart combination of various materials with optimized properties, preferably with reduced weight and long-term stability and employable under extreme conditions, such as high temperatures or a corrosive ambience. Whereas conventional alloys often do not satisfy these requirements, special alloys may be suitable due to their vast flexibility of composition and associated microstructures, often allowing to reach incredible mechanical properties and corrosion resistance, among various other interesting features such as shape memory, giant magnetoresistance, or even high-temperature superconductivity.

However, special alloys may themselves be materials of high complexity, and their interrelations with other system components may demand highly specific process conditions. Thus, for their wide applicability, it is necessary to deepen the basic understanding of their thermodynamic properties and structure and phase stability. This, in turn will allow predictions of the microstructural response and associated mechanical behaviour during processing and service.  

It is my pleasure to invite you to submit a manuscript for this Special Issue. Full experimental or numerical papers, communications, and reviews are all welcome.

Ass. Prof. Dr. Erwin Povoden-Karadeniz
Guest Editor

Manuscript Submission Information

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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. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

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Keywords

  • High strength
  • Corrosion resistance
  • High-temperature application, Nanoalloying, Solid Solutions
  • Intermetallics
  • Phase transformation

Published Papers (2 papers)

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Research

Open AccessArticle
Effects of the γ″-Ni3Nb Phase on Fatigue Behavior of Nickel-Based 718 Superalloys with Different Heat Treatments
Materials 2019, 12(23), 3979; https://doi.org/10.3390/ma12233979 - 30 Nov 2019
Abstract
The effects of the γ″-Ni3Nb phase on fatigue behavior of nickel-based 718 superalloys with standard heat treatment, hot isostatic pressing + solution treatment + aging, and hot isostatic pressing + direct aging were investigated by scanning electron microscope, transmission electron microscopy, [...] Read more.
The effects of the γ″-Ni3Nb phase on fatigue behavior of nickel-based 718 superalloys with standard heat treatment, hot isostatic pressing + solution treatment + aging, and hot isostatic pressing + direct aging were investigated by scanning electron microscope, transmission electron microscopy, and fatigue experiments. The standard heat treatment, hot isostatic pressing + solution treatment + aging, and hot isostatic pressing + direct aging resulted in the formation of more and smaller γ″ phases in the matrix in the nickel-based 718 superalloys. However, the grain boundaries of the hot isostatic pressing + direct aging sample showed many relatively coarse disk-like γ″ phases with major axes of ~80 nm and minor axes of ~40 nm. The hot isostatic pressing + direct aging sample with a stress amplitude of 380 MPa showed the longest high cycle fatigue life of 5.16 × 105 cycles. Laves phases and carbide inclusions were observed in the crack initiation zone, and the cracks propagated along the acicular δ phases in the nickel-based 718 superalloys. The precipitation of fine γ″ phases in the matrix and relatively coarse γ″ phases in the grain boundaries of the hot isostatic pressing + direct aging sample can hinder the movement of dislocation. Full article
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Open AccessArticle
Effect of Long-Time Annealing at 1000 °C on Phase Constituent and Microhardness of the 20Co-Cr-Fe-Ni Alloys
Materials 2019, 12(10), 1700; https://doi.org/10.3390/ma12101700 - 25 May 2019
Cited by 1
Abstract
The phase constituent and microhardness of the arc-melted 20Co-Cr-Fe-Ni alloys, in both as-cast state and after annealing at 1000 °C for 30 days, were experimentally investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Experiment results indicated that a uniform, stable, single [...] Read more.
The phase constituent and microhardness of the arc-melted 20Co-Cr-Fe-Ni alloys, in both as-cast state and after annealing at 1000 °C for 30 days, were experimentally investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Experiment results indicated that a uniform, stable, single Face-Center Cubic (FCC) phase can be obtained in as-cast 20 Co-Cr-Fe-Ni alloys with less than 30 at.% Cr. Annealing at 1000 °C has no effect on their phase composition and microhardness. When the Cr content is above 40 at.%, the σ phase forms and its volume fraction increases with the Cr content, which leads to an increase in microhardness. Annealing at 1000 °C for 30 days can slightly decrease the volume fraction of the σ phase and slightly decrease the alloy microhardness. Except for the Fe-rich alloys, the alloy microhardness increases with the Cr content when the Co and Ni or the Co and Fe contents were fixed. Moreover, comparing with the thermodynamically calculated phase diagram based on the TCFE database, it has been proved that the calculation can predict the phase stability of the FCC phase and the 1000 °C isothermal section. However, it fails to predict the stability of the σ phase near the liquidus. The present results will help to design and process treatment of the Co-Cr-Fe-Ni based high entropy alloys. Full article
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