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Crystals
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Crystallography of Structural Phase Transformations (Volume II)
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Crystallography of Structural Phase Transformations (Volume II)

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystal Engineering".

Deadline for manuscript submissions: closed (16 September 2022) | Viewed by 8426

Special Issue Editors

Dr. Cyril Cayron

E-Mail Website
Guest Editor
Swiss Federal Institute of Technology EPFL, Lausanne, Lausanne, Switzerland
Interests: metallurgy; EBSD; TEM; crystallography; martensitic transformations; twinning; variants; group theory
Special Issues, Collections and Topics in MDPI journals
Dr. Junfeng Xiao

E-Mail Website
Guest Editor
Swiss Federal Institute of Technology EPFL, Lausanne, Lausanne, Switzerland
Interests: crystallography; martensitic transformations; alloy

Special Issue Information

Dear Colleagues,

Solid–solid phase transformations generally imply a crystallographic orientation relationship (OR). The precipitates at the nucleation stage are often in OR with the surrounding matrix, martensite products are in OR with their parent austenite, and annealing twins and deformation twins are two crystals of the same species linked by an OR. The symmetries of the phases combined with the OR generate complex microstructures made of variants or twins that can be described mathematically with group theory, linear algebra, coset and multiple cosets, graphs, groupoids, high-dimension spaces, etc. Many efforts have been devoted over the last century to establishing bridges between this “descriptive” crystallography and the “predictive” thermodynamics, but full unification remains to be achieved. For the moment, the models are not well balanced. On the crystallographic side, the phenomenological of theory of martensitic crystallography (PTMC), the edge-to-edge matching model, the disconnection “topological” model, etc. are well developed, but they are often limited to using the generalized Clausius–Clapeyron formula to make the link with thermodynamics. On the thermodynamic side, one can find the famous Landau and Ginzburg–Landau theories, but crystallographic complexity is often reduced to the symmetries of the polynomial form of the free energy introduced with group representation theory. It is not easy to find a way to marry all the different approaches, even if phase field has made great progress over the last several decades.

As it is important for research in this field to continue, all experimental and theoretical contributions about phase transformations and crystallography are welcome in this Special Issue, regardless of the type of material (piezo- and ferroelectrics, structurally hardened alloys, martensitic alloys, ordered alloys, shape-memory alloys, polymorphic minerals, mechanically twinned materials, etc.).

Dr. Cyril Cayron
Dr. Junfeng Xiao
Guest Editors

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. Crystals 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

  • phase transformation
  • twins
  • variants
  • algebra
  • orientation relationship

Published Papers (4 papers)

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12 pages, 4749 KiB  
Article
Structural Phase Transformations in Detonation Coatings Based on Ti3SiC2 after Pulse-Plasma Effect
by Bauyrzhan Rakhadilov, Dauir Kakimzhanov, Dastan Buitkenov, Saule Abdulina, Laila Zhurerova and Zhuldyz Sagdoldina
Crystals 2022, 12(10), 1388; https://doi.org/10.3390/cryst12101388 - 29 Sep 2022
Cited by 2 | Viewed by 1045
Abstract
This work presents the results of the study on the effect of pulse-plasma treatment on the structural-phase states of the surface layer of detonation coatings based on Ti3SiC2. Structural-phase studies were carried out by three main methods: scanning electron [...] Read more.
This work presents the results of the study on the effect of pulse-plasma treatment on the structural-phase states of the surface layer of detonation coatings based on Ti3SiC2. Structural-phase studies were carried out by three main methods: scanning electron microscopy, transmission electron diffraction microscopy on thin foils and X-ray structural analysis. It was determined that after the pulse-plasma treatment, an increase in the intensity of the Ti3SiC2 peaks was observed, and the appearance of new reflections (101, 102, 112, 204, 1110, 0016) of this phase was detected, which indicates the increase in the MAX-phase content. It was determined that after the pulse-plasma treatment, the fraction of voids (pores) and the particle area decreased and the microstructure became more homogeneous, which resulted in the densification of the Ti3SiC2-based detonation coating. It was found that the process of detonation spraying with subsequent pulse-plasma treatment resulted in the formation of a Ti3SiC2-based coating, with TSC carbosilicide (Ti3SiC2) 0] plane reflexes, lamellar layered structure, and reduced porosity. Full article
(This article belongs to the Special Issue Crystallography of Structural Phase Transformations (Volume II))
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24 pages, 5744 KiB  
Article
Interplay between Habit Plane and Orientation Relationship in an Electron Backscatter Diffraction Analysis: Using the Example of η′-Al8Fe3 in η-Al5Fe2
by Hanka Becker, Ralf Hielscher and Andreas Leineweber
Crystals 2022, 12(6), 813; https://doi.org/10.3390/cryst12060813 - 08 Jun 2022
Cited by 4 | Viewed by 2083
Abstract
The Al5Fe2 intermetallic rouses interest due to its rapid formation at the interface between iron/steel and aluminum by reactive interdiffusion. Only in the last few years have the differently ordered states of that intermetallic been elucidated (η′, η″, η‴ and [...] Read more.
The Al5Fe2 intermetallic rouses interest due to its rapid formation at the interface between iron/steel and aluminum by reactive interdiffusion. Only in the last few years have the differently ordered states of that intermetallic been elucidated (η′, η″, η‴ and ηm). In the present work, the microstructural characteristics of the plate-shaped η′-Al8Fe3 phase regions in a η‴/η-phase matrix were investigated, determining the habit planes from two-dimensional electron backscatter diffraction (EBSD) maps. Within an η grain, there are altogether four variants of η′ with four characteristically crystallographic equivalent habit planes with respect to η. These habit planes have been determined based on their traces measured for differently oriented η containing the η′ plates, applying different methods. One method in particular makes use of the connection between orientation relationship and habit planes. Using these methods, the habit planes were determined as {hkl}η and {hkl}η′, both with {1 1.8 2.5}η/η′. Thus, essential characteristics of the microstructure are provided for further analysis of the phase transformation of the η phase to the η′-Al8Fe3 phase. Full article
(This article belongs to the Special Issue Crystallography of Structural Phase Transformations (Volume II))
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38 pages, 9524 KiB  
Article
The Correspondence Theory and Its Application to NiTi Shape Memory Alloys
by Cyril Cayron
Crystals 2022, 12(2), 130; https://doi.org/10.3390/cryst12020130 - 18 Jan 2022
Cited by 9 | Viewed by 1976
Abstract
Martensite crystallography is usually described by the phenomenological theory of martensite crystallography (PTMC). This theory relies on stretch matrices and compatibility equations, but it does not give a global view on the structures of variants, and it masks the relative roles of the [...] Read more.
Martensite crystallography is usually described by the phenomenological theory of martensite crystallography (PTMC). This theory relies on stretch matrices and compatibility equations, but it does not give a global view on the structures of variants, and it masks the relative roles of the symmetries and metrics. Here, we propose an alternative theory called correspondence theory (CT) based on correspondences and symmetries. The compatibility twins between the martensite variants are inherited by correspondence from the symmetry elements of austenite. We show that, for the B2 to B19′ transformation, there is a one-to-one relation between the specific misorientations and the specific inter-correspondences between the variants. For each type of misorientation, the twin of its junction plane can be predicted without calculating the stretch matrices, as in PTMC. The rational elements of the twins do not depend on the metrics; all the transformation twins are thus “generic”. We also introduce the concept of a weak plane that permits to explain the junction planes for polar pairs of variants for which the PTMC compatibility equations cannot be solved. The predictions are validated by comparison with experimental Transmission Kikuchi Diffraction (TKD) maps. Full article
(This article belongs to the Special Issue Crystallography of Structural Phase Transformations (Volume II))
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18 pages, 4034 KiB  
Article
Crystal Structure, Microstructure and Electronic Properties of a Newly Discovered Ternary Phase in the Al-Cr-Sc System
by Monika Kušter, Anton Meden, Boštjan Markoli, Zoran Samardžija, Maja Vončina, Pascal Boulet, Émilie Gaudry, Jean-Marie Dubois and Sašo Šturm
Crystals 2021, 11(12), 1535; https://doi.org/10.3390/cryst11121535 - 09 Dec 2021
Cited by 1 | Viewed by 2565
Abstract
This study focused on the crystal and electronic structures of a newly discovered phase in the Al-Cr-Sc system. The latter two species do not mix in a binary alloy, but can be alloyed with aluminium in the vicinity of the Al2−xCr [...] Read more.
This study focused on the crystal and electronic structures of a newly discovered phase in the Al-Cr-Sc system. The latter two species do not mix in a binary alloy, but can be alloyed with aluminium in the vicinity of the Al2−xCrxSc composition, where 0.3 < x < 0.5. After preparation of the pure constituents via arc melting, high-temperature annealing at 990 °C for 240 h was required to achieve full mixing of the elements. A detailed characterisation of the crystal structure, alloy microstructure and stability was obtained using single-crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD), in addition to transmission electron microscopy (TEM), especially in high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) mode, scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDXS) and differential scanning calorimetry (DSC) measurements. The crystal structure was refined to a hexagonal unit cell of the MgZn2 type, space group no. 194, P63/mmc, which belongs to the Laves phases family. Special attention was paid to the occupancy of the crystallographic sites that were filled by both Cr and Al atoms. First-principles calculations based on the density functional theory (DFT) were performed to investigate the electronic structure of this ternary phase. The total density of states (DOS) exhibited a pronounced sp character, where a shallow pseudo-gap was visible 0.5 eV below the Fermi energy that brought a small but definite contribution to the thermodynamic stability of the compound. Full article
(This article belongs to the Special Issue Crystallography of Structural Phase Transformations (Volume II))
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