Transformation Texture and Its Prediction in Cubic and Hexagonal Metals

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

Deadline for manuscript submissions: 31 August 2024 | Viewed by 8688

Special Issue Editor


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Guest Editor
Frontier Research Center for Applied Atomic Science, Ibaraki University, Naka 319-1106, Japan
Interests: texture; variant selection; phase transformation

Special Issue Information

Dear Colleagues,

Crystallographic textures that develop during phase transformation are one of the key factors to improve the plastic, elastic, magnetic, as well as electrical properties of various cubic and hexagonal metals such as steels and titanium and zirconium alloys that have been vastly used in automobile, electrical, biomedical, aerospace, atomic energy, as well as heavy industries. Since phase transformation in such materials is mostly caused by high-temperature heating processes, austenization, austempering, solution in a beta phase, etc., in situ texture measurements are difficult so that the responsible mechanisms for developing transformation texture are still a central subject in this filed. Today, modern facilities of pulsed neutrons and high energy synchrotron radiation allow us to directly observe the change of textures during phase transformation under various conditions at a time resolution even below 60 s, and thus, the mechanisms and the ways to predict transformation textures have been gradually known. This Special Issue covers all areas of experimental and theoretical research on transformation textures of metals and alloys with cubic and hexagonal lattice structures, including experiments via not only in situ measurements but also ex situ electron back scattering diffraction and conventional X-ray measurements of textures and theoretical works based on such measurements. Research on materials processed by various methods such as additive manufacturing is welcome.

Dr. Toshiro Tomida
Guest Editor

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Keywords

  • phase transformation
  • crystallographic texture
  • transformation texture prediction
  • hexagonal metals
  • cubic metals
  • steel
  • titanium alloy
  • zirconium alloy
  • pulsed neutron
  • synchrotron radiation

Published Papers (4 papers)

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Research

16 pages, 6895 KiB  
Article
Application of Transformation Treatment to Commercial Low-Grade Electrical Steels under Different Processing Conditions
by Ping Yang, Dandan Ma, Jinhua Wang, Shufang Pang and Xinfu Gu
Metals 2022, 12(10), 1628; https://doi.org/10.3390/met12101628 - 28 Sep 2022
Viewed by 1125
Abstract
In this paper, two low-grade electrical steels are used to inspect the effect of initial columnar grains and final transformation treatment on the microstructure and textures. Results show that the Al and P elements, besides causing the surface oxidation or segregation, increase the [...] Read more.
In this paper, two low-grade electrical steels are used to inspect the effect of initial columnar grains and final transformation treatment on the microstructure and textures. Results show that the Al and P elements, besides causing the surface oxidation or segregation, increase the critical transformation temperatures of steels, thus restricting the formation of strong {100} texture. Two-layer grain structure of typical surface-effect-induced transformation is developed in the steels without Al. The transformation textures in both steels are nearly random, which are much better than the {111} recrystallization texture or the memory type of transformation texture. The steel with initial columnar grained structure produces more {110}-oriented grains in finally transformed sheets, whereas the initial hot-rolled structure induces more {100}-oriented grains. In addition, high cold rolling reduction produces a one-layer grain structure in the final transformed sheets. It is confirmed again that the increase in final heating temperature leads to a transition from the memory type of transformation texture to surface-effect-induced transformation texture. For commercial steels containing harmful Al and P, the change in processing parameters during transformation treatment does not influence transformed structure and texture. Finally, the combined control of three stages of transformation during casting, hot rolling and final annealing is discussed. Full article
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11 pages, 6508 KiB  
Article
The Role of Parent Phase Topology in Double Young–Kurdjumow–Sachs Variant Selection during Phase Transformation in Low-Carbon Steels
by Leo A. I. Kestens, Tuan Nguyen-Minh and Roumen H. Petrov
Metals 2022, 12(6), 939; https://doi.org/10.3390/met12060939 - 30 May 2022
Cited by 4 | Viewed by 1656
Abstract
The present paper investigates the role of parent phase topology on a crystallographic variant selection rule. This rule assumes that product phase nuclei appear at certain grain boundaries in the parent structure, such that a specific crystallographic orientation relationship is observed with both [...] Read more.
The present paper investigates the role of parent phase topology on a crystallographic variant selection rule. This rule assumes that product phase nuclei appear at certain grain boundaries in the parent structure, such that a specific crystallographic orientation relationship is observed with both parent grains at either side of the grain boundary. The specific crystallographic orientation correspondence considered here is the Young–Kurdjumow–Sachs (YKS) orientation relationship <112>90° (which exhibits 24 symmetrical equivalents). The aforementioned relationship is characteristic of phase transformations in low-carbon steel grades. It is shown that, for different parent phase textures, ~20% of the grain boundaries comply with the double YKS condition allowing for a tolerance of 5°, ignoring the presence of topology in the parent phase microstructure. The presented model allows for connecting the presence of a specific parent phase topology with the condition of the double YKS variant selection rule in a number of practical cases: (i) for hot rolled Ti–Interstitial Free (IF) steel with and without Mn addition, (ii) for cold rolled IF steel exhibiting very strong texture memory after forward and reverse α ⇌ γ phase transformation and (iii) for a martensitic transformation in a Fe–8.5% Cr steel. It is shown that the double YKS variant selection criterion may explain several specific features of the observed transformation textures, while assuming a non-correlated arbitrary pair topology of the parent austenite structure (implying that for N parent orientations N/2 pairs are selected in an arbitrary manner). Full article
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18 pages, 5931 KiB  
Article
Property Improvement of Additively Manufactured Ti64 by Heat Treatment Characterized by In Situ High Temperature EBSD and Neutron Diffraction
by Shigehiro Takajo, Toshiro Tomida, El’ad N. Caspi, Asaf Pesach, Eitan Tiferet and Sven C. Vogel
Metals 2021, 11(10), 1661; https://doi.org/10.3390/met11101661 - 19 Oct 2021
Cited by 5 | Viewed by 2799
Abstract
Among various off-equilibrium microstructures of additively manufactured Ti-6Al-4V alloy, electron beam powder bed fusion, in which three dimensional metallic objects are fabricated by melting the ingredient powder materials layer by layer on a pre-heated bed, results in a specimen that is nearly free [...] Read more.
Among various off-equilibrium microstructures of additively manufactured Ti-6Al-4V alloy, electron beam powder bed fusion, in which three dimensional metallic objects are fabricated by melting the ingredient powder materials layer by layer on a pre-heated bed, results in a specimen that is nearly free of the preferred orientation of the α-Ti phase as well as a low beta phase fraction of ~1 wt%. However, when further heat treatment of up to 1050 °C was applied to the material in our previous study, a strong texture aligning the hexagonal basal plane of α phase with the build direction and about 6% β phase appeared at room temperature. In this study, to understand the mechanism of this heat treatment, the grain level microstructure of the additively manufactured Ti-6Al-4V was investigated using in situ high temperature EBSD up to 1000 °C, which allows the tracking of individual grains during a heat cycle. As a result, we found a random texture originating from the fine grains in the initial material and observed a significant suppression of α phase nucleation in the slow cooling after heating to 950 °C within the α and β dual phase regime but close to the the β-transus temperature at ~980 °C, which led to a coarse microstructure. Furthermore, the texture resulting from phase transformation of the additively manufactured Ti-6Al-4V assuming nucleation at the grain boundaries was modeled, using the double Burgers orientation relationship for the first time. The model successfully reproduced the measured texture, suggesting that the texture enhancement of the α phase by the additional heat treatment derives also from the variant selection during the phase transformation and nucleation on grain boundaries. Full article
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25 pages, 32273 KiB  
Article
Texture Memory in Hexagonal Metals and Its Mechanism
by Toshiro Tomida, Sven C. Vogel, Yusuke Onuki and Shigeo Sato
Metals 2021, 11(10), 1653; https://doi.org/10.3390/met11101653 - 18 Oct 2021
Cited by 4 | Viewed by 2056
Abstract
Texture memory is a phenomenon in which retention of initial textures occurs after a complete cycle of forward and backward transformations, and it occurs in various phase-transforming materials including cubic and hexagonal metals such as steels and Ti and Zr alloys. Texture memory [...] Read more.
Texture memory is a phenomenon in which retention of initial textures occurs after a complete cycle of forward and backward transformations, and it occurs in various phase-transforming materials including cubic and hexagonal metals such as steels and Ti and Zr alloys. Texture memory is known to be caused by the phenomena called variant selection, in which some of the allowed child orientations in an orientation relationship between the parent and child phases are preferentially selected. Without such variant selection, the phase transformations would randomize preferred orientations. In this article, the methods of prediction of texture memory and mechanisms of variant selections in hexagonal metals are explored. The prediction method using harmonic expansion of orientation distribution functions with the variant selection in which the Burgers orientation relationship, {110}β//{0001}α-hex <11¯1>β//21¯1¯0α-hex, is held with two or more adjacent parent grains at the same time, called “double Burgers orientation relation (DBOR)”, is introduced. This method is shown to be a powerful tool by which to analyze texture memory and ultimately provide predictive capabilities for texture changes during phase transformations. Variation in nucleation and growth rates on special boundaries and an extensive growth of selected variants are also described. Analysis of textures of commercially pure Ti observed in situ by pulsed neutron diffraction reveals that the texture memory in CP-Ti is indeed quite well predicted by consideration of the mechanism of DBOR. The analysis also suggests that the nucleation and growth rates on the special boundary of 90° rotation about 21¯1¯0α-hex should be about three times larger than those of the other special boundaries, and the selected variants should grow extensively into not only one parent grain but also other grains in α-hex(hexagonal)→β(bcc) transformation. The model calculations of texture development during two consecutive cycles of α-hexβα-hex transformation in CP-Ti and Zr are also shown. Full article
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