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

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

Deadline for manuscript submissions: closed (30 June 2021) | Viewed by 9585

Special Issue Editor

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, Vienna, Austria
Interests: metastable phases; special alloy systems; intermetallics; precipitate evolution; functional materials; heterogeneous systems
Special Issues, Collections and Topics in MDPI journals

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

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. Materials is an international peer-reviewed open access semimonthly 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

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

Published Papers (3 papers)

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Research

15 pages, 5445 KiB  
Article
Influence of Cr, Mn, Co and Ni Addition on Crystallization Behavior of Al13Fe4 Phase in Al-5Fe Alloys Based on ThermoDynamic Calculations
by Na Pang, Zhiming Shi, Cunquan Wang, Ninyu Li and Yaming Lin
Materials 2021, 14(4), 768; https://doi.org/10.3390/ma14040768 - 06 Feb 2021
Cited by 5 | Viewed by 2400
Abstract
Alloying is an effective method to refine coarse grains of an Al13Fe4 phase and strengthen Al-Fe alloys. However, the grain refinement mechanism remains unclear in terms of the thermodynamics. Herein, the influence of M-element, i.e., Cr, Mn, Co and [...] Read more.
Alloying is an effective method to refine coarse grains of an Al13Fe4 phase and strengthen Al-Fe alloys. However, the grain refinement mechanism remains unclear in terms of the thermodynamics. Herein, the influence of M-element, i.e., Cr, Mn, Co and Ni, addition on the activity of Al and Fe atoms, Gibbs free energy of the Al13Fe4 nucleus in Al-Fe melt and the formation enthalpy of an Al13Fe4 phase in Al-Fe alloys is systematically investigated using the extended Miedema model, Wilson equation, and first-principle calculations, respectively. The results reveal that the addition of different M elements increases the activity of Fe atoms and reduces the Gibbs free energy of the Al13Fe4 nucleus in Al-Fe melt, where the incorporation of Ni renders the most obvious effect, followed by Mn, Co, and Cr. Additionally, the formation enthalpy decreases in the following order: Al78(Fe23Cr) > Al78(Fe23Mn) > Al13Fe4 > Al78(Fe23Ni) > Al78(Fe23Co), where the formation enthalpy of Al78(Fe23Ni) is close to Al78(Fe23Co). Moreover, the presence of Ni promotes the nucleation of the Al13Fe4 phase in Al-Fe alloys, which reveals the mechanism of grain refinement from a thermodynamics viewpoint. Full article
(This article belongs to the Special Issue Thermodynamic Properties, Structure and Phase Stabilities of Special Alloys)
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12 pages, 5666 KiB  
Article
Effects of the γ″-Ni3Nb Phase on Fatigue Behavior of Nickel-Based 718 Superalloys with Different Heat Treatments
by Li-Shi-Bao Ling, Zheng Yin, Zhi Hu, Jun Wang and Bao-De Sun
Materials 2019, 12(23), 3979; https://doi.org/10.3390/ma12233979 - 30 Nov 2019
Cited by 7 | Viewed by 3112
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
(This article belongs to the Special Issue Thermodynamic Properties, Structure and Phase Stabilities of Special Alloys)
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12 pages, 3561 KiB  
Article
Effect of Long-Time Annealing at 1000 °C on Phase Constituent and Microhardness of the 20Co-Cr-Fe-Ni Alloys
by Changjun Wu, Ya Sun, Ya Liu and Hao Tu
Materials 2019, 12(10), 1700; https://doi.org/10.3390/ma12101700 - 25 May 2019
Cited by 6 | Viewed by 3449
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
(This article belongs to the Special Issue Thermodynamic Properties, Structure and Phase Stabilities of Special Alloys)
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