Special Issue "X-ray and neutron Line Profile Analysis of Microstructures"

A special issue of Crystals (ISSN 2073-4352).

Deadline for manuscript submissions: closed (15 January 2020).

Special Issue Editors

Prof. Emeritus Tamás Ungár
Website
Guest Editor
Department of Materials Physics, Eötvös Loránd University Budapest, PO Box 32, H-1518 Budapest, Hungary
at present at: School of Materials, The University of Manchester, Manchester, UK
Interests: line broadening; domain size; crystallite size; dislocations; microstrains; intergranular strains effect on line broadening; texture effect on line broadening; geometrically necessary dislocations; submicron grain size
Dr. Gábor Ribárik
Website
Guest Editor
Department of Materials Physics, Eötvös Loránd University Budapest, PO Box 32, H-1518 Budapest, Hungary

Special Issue Information

Dear Colleagues,

X-ray and neutron line profile analysis proves to be an ever more powerful method to reveal many different quantitative aspects of microstructure properties in crystalline materials. It has become one of the most widely used complementary tools to electron microscopy for characterizing microstructures of materials. Functional properties of crystalline materials are determined by both the crystal structure and the imperfectness of crystal structure, where imperfectness comprises of a large variety of lattice defects. When the crystal lattice becomes imperfect diffraction peaks broaden and the kind and type of broadening also reveals great variety. Coherently scattering domains gives size broadening, dislocations, intergranular strains, thermal anisotropy in non-cubic crystals or misfit between matrix and second-phase particles produce strain broadening, planar defects of different kinds make peaks shift and broaden, chemical inhomogeneities on different scales produce specific peak shifts and shapes. All these effects can combine in various manners. On top of all that peaks can not only broaden but also become asymmetric. The vast variety of peak broadening, shift and shape is the topic of line profile analysis. Entanglement of the different causes in complex appearance of line profile patterns is the art of line profile analysis. All contributions are invited which can correlate diffraction patterns of imperfect crystalline materials with specific lattice defects. The method of obtaining lattice defect types and quantities from analysing diffraction patterns is very welcome. The relevance of specified lattice defects to fundamental materials properties is especially appreciated. Modeling diffraction patterns corresponding to different lattice defects is most welcome.

Prof. Emeritus Tamás Ungár
Dr. Gábor Ribárik
Guest Editors

Manuscript Submission Information

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Keywords

  • X-ray line broadening
  • neutron line broadening
  • size broadening
  • strain broadening
  • residual internal strains
  • intergranular strains
  • chemical heterogeneities
  • modeling diffraction patterns
  • texture and line profiles

Published Papers (6 papers)

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Research

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Open AccessArticle
Microstructure Characterization in Individual Texture Components by X-Ray Line Profile Analysis: Principles of the X-TEX Method and Practical Application to Tensile-Deformed Textured Ti
Crystals 2020, 10(8), 691; https://doi.org/10.3390/cryst10080691 - 10 Aug 2020
Abstract
A novel X-ray diffraction-based method and computer program X-TEX has been developed to determine the microstructure in individual texture components of polycrystalline, textured materials. Two different approaches are presented. In the first one, based on the texture of the specimen, the X-TEX software [...] Read more.
A novel X-ray diffraction-based method and computer program X-TEX has been developed to determine the microstructure in individual texture components of polycrystalline, textured materials. Two different approaches are presented. In the first one, based on the texture of the specimen, the X-TEX software provides optimized specimen orientations for X-ray diffraction experiments in which diffraction peaks consist of intensity contributions stemming from grain populations of separate texture components in the specimen. Texture-specific diffraction patterns can be created by putting such peaks together from different measurements into an artificial pattern for each texture component. In the second one, the X-TEX software can determine the intensity contributions of different texture components to diffraction peaks measured in a particular sample orientation. According to this, peaks belonging mainly to one of the present texture components are identified and grouped into the same quasi-phase during the evaluation procedure. The X-TEX method was applied and tested on tensile-deformed, textured, commercially pure titanium samples. The patterns were evaluated by the convolutional multiple whole profile (CMWP) procedure of line profile analysis for dislocation densities, dipole character, slip systems and subgrain size for three different texture components of the Ti specimens. Significant differences were found in the microstructure evolution in the two major and the random texture components. The dislocation densities were discussed by the Taylor model of work hardening. Full article
(This article belongs to the Special Issue X-ray and neutron Line Profile Analysis of Microstructures)
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Open AccessArticle
The Convolutional Multiple Whole Profile (CMWP) Fitting Method, a Global Optimization Procedure for Microstructure Determination
Crystals 2020, 10(7), 623; https://doi.org/10.3390/cryst10070623 - 17 Jul 2020
Abstract
The analysis of line broadening in X-ray and neutron diffraction patterns using profile functions constructed on the basis of well-established physical principles and TEM observations of lattice defects has proven to be a powerful tool for characterizing microstructures in crystalline materials. These principles [...] Read more.
The analysis of line broadening in X-ray and neutron diffraction patterns using profile functions constructed on the basis of well-established physical principles and TEM observations of lattice defects has proven to be a powerful tool for characterizing microstructures in crystalline materials. These principles are applied in the convolutional multiple-whole-profile (CMWP) procedure to determine dislocation densities, crystallite size, stacking fault and twin boundary densities, and intergranular strains. The different lattice defect contributions to line broadening are separated by considering the hkl dependence of strain anisotropy, planar defect broadening and peak shifts, and the defect dependent profile shapes. The Levenberg–Marquardt (LM) peak fitting procedure can be used successfully to determine crystal defect types and densities as long as the diffraction patterns are relatively simple. However, in more complicated cases like hexagonal materials or multiple-phase patterns, using the LM procedure alone may cause uncertainties. Here, we extended the CMWP procedure by including a Monte Carlo statistical method where the LM and a Monte Carlo algorithm were combined in an alternating manner. The updated CMWP procedure eliminated uncertainties and provided global optimized parameters of the microstructure in good correlation with electron microscopy methods. Full article
(This article belongs to the Special Issue X-ray and neutron Line Profile Analysis of Microstructures)
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Open AccessArticle
Deformation Induced Soft and Hard Lath Packets Enhance Ductility in Martensitic Steels
Crystals 2020, 10(5), 373; https://doi.org/10.3390/cryst10050373 - 06 May 2020
Cited by 1
Abstract
Martensitic steels are widely used structural materials with outstanding mechanical properties. Their high strength is provided by the non-diffusional phase transformation of fcc γ into thin lamellar bcc plates during fast cooling. Coherency strains between the fcc and bcc lamellae induce large dislocation [...] Read more.
Martensitic steels are widely used structural materials with outstanding mechanical properties. Their high strength is provided by the non-diffusional phase transformation of fcc γ into thin lamellar bcc plates during fast cooling. Coherency strains between the fcc and bcc lamellae induce large dislocation densities in the range of 1016 m−2, well above the densities attainable by conventional plastic deformation. Using high resolution X-ray line profile analysis, scanning electron microscopy, and hardness tests we show that during tensile deformation when the active Burgers vectors are within the lath plane the lath-packets work soften. On the contrary, when the active Burgers vectors are oblique to the lath-plane the lath-packets work harden. The softening and hardening processes in the differently oriented lath-packets produce a composite of hard and soft components on the length scale of lath-packet size. The stress–strain response of the alloy is discussed in terms of the different mean free paths and the different annihilation lengths of dislocations in the softened and hardened lath-packets. The relatively good ductility is shown to be produced by the composite microstructure induced by plastic strain. Full article
(This article belongs to the Special Issue X-ray and neutron Line Profile Analysis of Microstructures)
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Open AccessArticle
Phase and Residual Stress Evaluation of Dual-Phase Al70Cr30N and Al80Cr20N PVD Films
Crystals 2019, 9(7), 362; https://doi.org/10.3390/cryst9070362 - 15 Jul 2019
Abstract
We investigated arc ion-plated Al70Cr30N and Al80Cr20N thin films deposited with three different bias voltages (50 V, 100 V, and 150 V) to study crystal phase stabilities, residual stresses, and mechanical properties. Commercial compositions of [...] Read more.
We investigated arc ion-plated Al70Cr30N and Al80Cr20N thin films deposited with three different bias voltages (50 V, 100 V, and 150 V) to study crystal phase stabilities, residual stresses, and mechanical properties. Commercial compositions of AlxCr100–xN coatings typically range from x = 50 to 70 where the cubic face centered crystal phase occurs. The present study focuses on films near the solubility limit of Al in the cubic Cr(Al)N lattice around 70 at.%, above which hexagonal AlN (h–AlN) starts to form in significant amounts. Residual stress values are obtained by two methods: grazing incidence diffraction with the wholepattern fitting and the conventional side inclination method (sin2Ψ method). When multiple phases are present in the film, wholepattern fitting turns out to be particularly effective and a comparison of both measurement methods will be discussed. The Al70Cr30N films consist of the cubic phase with crystallite sizes of about 70 nm for all bias voltages. Compressive stress increased with bias voltage from about 3 to almost 6 GPa and coatings become brittle. Al80Cr20N films showed a different dependence on bias voltage. Using 50 V bias voltage in deposition, the major phase is h–AlN phase with a crystallite grain size of < 30 nm and (0002) preferred orientation. With increasing bias the cubic phase is stabilized also reaching about 70 nm crystallite size. In general, the compressive residual stress was significantly lower than for Al70Cr30N films for the same bias voltages which may be a result of the presence of the hexagonal phase. Wear and scratch tests confirmed higher ductility of the Al80Cr20N variants but reduced resistance of the films in impact wear testing. Full article
(This article belongs to the Special Issue X-ray and neutron Line Profile Analysis of Microstructures)
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Open AccessArticle
In-Situ Synchrotron Profile Analysis after High-Pressure Torsion Deformation
Crystals 2019, 9(5), 232; https://doi.org/10.3390/cryst9050232 - 29 Apr 2019
Cited by 6
Abstract
The presence of hydrostatic pressure is a general crucial characteristic of severe plastic deformation methods for reaching high strains and for introducing large quantities of lattice defects, which are necessary to establish new grain boundaries. Insights into the processes occurring during deformation and [...] Read more.
The presence of hydrostatic pressure is a general crucial characteristic of severe plastic deformation methods for reaching high strains and for introducing large quantities of lattice defects, which are necessary to establish new grain boundaries. Insights into the processes occurring during deformation and the influence of hydrostatic pressure are necessary to help better understand the SPD methods. A special experimental procedure was designed to simulate the hydrostatic pressure release: High pressure torsion (HPT)-deformed microstructure changes related to the release of hydrostatic pressure after the HPT deformation of copper and nickel were studied by freezing the sample before releasing the pressure. High-resolution in-situ X-ray diffraction of the heating process was performed using synchrotron radiation in order to apply X-ray line profile analysis to analyze the pressure release. The results on copper and nickel generally indicated the influence of hydrostatic pressure on the mobility and interaction of deformation-induced defects as well as the resulting microstructure. Full article
(This article belongs to the Special Issue X-ray and neutron Line Profile Analysis of Microstructures)
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Review

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Open AccessReview
Historical Perspective on Diffraction Line-Profile Analyses for Crystals Containing Defect Clusters
Crystals 2019, 9(5), 257; https://doi.org/10.3390/cryst9050257 - 17 May 2019
Cited by 2
Abstract
Deviations of crystal diffraction line profiles from those predicted by the dynamical theory of diffraction for perfect crystals provide a window into the microscopic distributions of defects within non-perfect crystals. This overview provides a perspective on key theoretical, computational, and experimental developments associated [...] Read more.
Deviations of crystal diffraction line profiles from those predicted by the dynamical theory of diffraction for perfect crystals provide a window into the microscopic distributions of defects within non-perfect crystals. This overview provides a perspective on key theoretical, computational, and experimental developments associated with the analysis of diffraction line profiles for crystals containing statistical distributions of point defect clusters, e.g., dislocation loops, precipitates, and stacking fault tetrahedra. Pivotal theoretical developments beginning in the 1940s are recalled and discussed in terms of their impact on the direction of theoretical and experimental investigations of lattice defects in the 1960s, the 1970s, and beyond, as both experimental and computational capabilities advanced. The evolution of experimental measurements and analysis techniques, as stimulated by theoretical and computational progress in understanding the distortion fields surrounding defect clusters, is discussed. In particular, consideration is given to determining dislocation loop densities and separate size distributions for vacancy and interstitial type loops, and to the internal strain and size distributions for coherent precipitates. Full article
(This article belongs to the Special Issue X-ray and neutron Line Profile Analysis of Microstructures)
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