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Crystals
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Mechanical Behaviour of Anisotropic Coarse Grain Materials
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Mechanical Behaviour of Anisotropic Coarse Grain Materials

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystalline Metals and Alloys".

Deadline for manuscript submissions: 15 September 2024 | Viewed by 1469

Special Issue Editors

Dr. Benedikt Engel

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Guest Editor
Gas Turbine and Transmission Research Centre, G2TRC, Faculty of Engineering, University of Nottingham, Nottingham NG7 2TU, UK
Interests: mechanical properties; mechanical behavior of materials; mechanical testing; microstructure; metals; high temperature materials; material characterization; failure analysis; SEM analysis; fracture mechanics
Dr. Christopher Hyde

E-Mail Website
Guest Editor
Department of M3, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK
Interests: mechanical properties; mechanical behavior of materials; mechanical testing; microstructure materials; material characterization; materials processing; advanced materials; mechanics of materials; material characteristics
Dr. Moritz Liesegang

E-Mail Website
Guest Editor
Institute of Materials Science and Engineering, RPTU Kaiserslautern-Landau, 67653 Kaiserslautern, Germany
Interests: materials science; mechanical behaviour; anisotropic materials; FE simulation; materials characterization; hybrid materials; ultrasonic welding; ultrasonic modification

Special Issue Information

Dear Colleagues,

The term “coarse” in coarse grain materials relates less to an actual grain size and more to the relation between the amounts of grains present in highly loaded areas of mechanical components. For small amounts of grains (less than 10) in failure-critical areas, high scatter in mechanical properties due to elastic and plastic anisotropies can occur. In order to compensate for the scatter, these material regions are often treated as isotropic (by assuming an average material behaviour), and high safety factors are added. To reduce safety factors and improve the performance and efficiency of the components, a better and deeper understanding of how coarse grain material reacts under loading is crucial. Some important questions arise here: How do grains interact with each other, especially if their stiffness is highly different? How does this affect the grains' fatigue behaviour? Which grain orientation or grain agglomeration tends to show more crack initiation? How does the mechanical behaviour of a grain affect the neighbouring grains? How do differently orientated grains react to the same creep loading? These questions can be answered by conducting extensive microscopic evaluations under loading conditions (in situ observation) by using digital image correlation (or similar), as well as complex numerical simulations using Voronoi tessellations, or even models of actual measured microstructures.

Thus, we invite researchers to contribute to this Special Issue of Crystals entitled “Mechanical behaviour of coarse grain materials”, focusing on the experimental and numerical investigations on the influence of grain orientation and interaction on the mechanical behaviour of coarse grain materials.

Dr. Benedikt Engel
Dr. Christopher Hyde
Dr. Moritz Liesegang
Guest Editors

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. 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

  • elastic anisptropy
  • plastic anisotropy
  • grain interaction
  • schmid factor
  • polycrystalline material
  • coarse grain
  • voronoi tesselation
  • digital image correlation
  • in-situ testing
  • deformation behaviour

Published Papers (2 papers)

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Research

10 pages, 6361 KiB  
Article
Fatigue Analysis of the Nickel-Based Superalloy Inconel 617 by Fatigue Experiments and EBSD Data-Based Finite Element Simulations in Correlation with E·m Theories
by Moritz Liesegang and Tilmann Beck
Crystals 2024, 14(4), 356; https://doi.org/10.3390/cryst14040356 - 10 Apr 2024
Viewed by 322
Abstract
Nickel-based superalloys exhibit pronounced elastic anisotropy and, hence, the local grain orientation strongly affects the stress and strain distribution in the material under mechanical loadings. Therefore, the crack initiation and failure behaviour of components made from nickel-based superalloys are complex and hardly predictable. [...] Read more.
Nickel-based superalloys exhibit pronounced elastic anisotropy and, hence, the local grain orientation strongly affects the stress and strain distribution in the material under mechanical loadings. Therefore, the crack initiation and failure behaviour of components made from nickel-based superalloys are complex and hardly predictable. A better fundamental understanding of the phenomena that occur in nickel-based superalloys under a quasistatic and cyclic load is therefore desired. Previously, a continuum mechanics-based model has been successfully developed, considering the grain structure, the elastic anisotropy, and the Schmid factor, based on data from electron backscatter diffraction (EBSD). The E·m model was confirmed by the finite element method (FEM) simulations and experimental observations regarding the resulting average stresses and strains in the individual grains as well as the formation of slip bands under a quasistatic load with few restrictions. The behaviour under cyclic loadings has been investigated in this work to correlate the mechanical behaviour, simulated by the previously developed FE models, with the local stiffness and Schmid factors considering fatigue failure. For this purpose, the fatigue behaviour of Inconel 617 samples was characterised up to the high-cycle fatigue (HCF) regime, accompanied by EBSD measurements for stress amplitudes that resulted in strains close to the elastic–plastic regime. The EBSD data were used to create digital twins of the samples to simulate the mechanical reaction to a displacement similar to the associated strain of the fatigue tests. An analysis of the fractured samples by scanning electron microscopy was performed to retrace the location of the crack initiation supported by the EBSD measurements before and after fatigue testing. Two samples were investigated in detail that showed different fracture types. Sample 1 showed transcrystalline failure in a grain that showed a high Young’s modulus, Schmid factor, and resolved shear stress that indicates a failure due to the properties of the grain itself. In contrast, an intercrystalline failure was observed for sample 2 that showed large differences in the orientation and, hence, largely different mechanical properties in the area of failure as well. The observed failure types, the resulting stresses and strains calculated by the FE model, and the consideration of the E·m model showed an agreement of all the methods. Therefore, the findings of this work complement previous investigations of the mechanical behaviour of coarse-grained anisotropic nickel-based superalloys with a focus on the orientations of the grains towards the loading direction. Full article
(This article belongs to the Special Issue Mechanical Behaviour of Anisotropic Coarse Grain Materials)
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Graphical abstract

10 pages, 5462 KiB  
Article
Identification of Intermetallic Phases Limiting the Growth of Austenite Grains in the Low-Pressure Carburizing Process
by Konrad Dybowski and Leszek Klimek
Crystals 2023, 13(12), 1683; https://doi.org/10.3390/cryst13121683 - 14 Dec 2023
Cited by 1 | Viewed by 832
Abstract
This article presents the results of a study to identify intermetallic phases whose role is to limit austenite grain growth in the low-pressure carburizing process. A drawback of high-temperature low-pressure carburizing is the austenite grain growth during the process. Using low-pressure carburizing with [...] Read more.
This article presents the results of a study to identify intermetallic phases whose role is to limit austenite grain growth in the low-pressure carburizing process. A drawback of high-temperature low-pressure carburizing is the austenite grain growth during the process. Using low-pressure carburizing with pre-nitriding technology (PreNitLPC®) offers the possibility of reducing austenite grain growth. This technology involves the application of doses of ammonia during the heating stage of the steel, at the carburizing temperature, to introduce nitrogen into the surface layer of the steel and to form nitrides. It is these phases that cause restrictions on austenite grain growth during carburizing. The research carried out in this article was aimed at identifying these phases. The research was carried out on one of the basic steels used for carburizing—16MnCr5 steel. The carburizing of this steel with and without pre-nitriding was performed, followed by an evaluation of the austenite grain size after these processes and the identification of the intermetallic phases present in the surface layer of the steel. Full article
(This article belongs to the Special Issue Mechanical Behaviour of Anisotropic Coarse Grain Materials)
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