| 1. |
- Ameyama, Kei, et al.
(författare)
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Harmonic structure, a promising microstructure design
- 2022
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Ingår i: Materials Research Letters. - : Informa UK Limited. - 2166-3831. ; 10:7, s. 440-471
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Tidskriftsartikel (refereegranskat)abstract
- The harmonic structure is a recently introduced concept paving the way for engineering metallic materials to achieve excellent mechanical performance. They consist of soft coarse-grained regions (Core) that are three-dimensionally surrounded by a connected network of hard ultra-fine grained regions (Shell). The interaction in these Core–Shell regions produces a synergistic effect, during plastic deformation, leading to superior mechanical properties that are extremely important in practical applications. The current review paper is aimed at providing a critical assessment on this novel concept of microstructure design. It also involves the identification and critical discussion of key issues which deserve additional studies.
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| 2. |
- Chatellier, Joséphine, et al.
(författare)
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Mechanics of accelerated strain hardening in harmonic-structure materials
- 2022
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Ingår i: 42nd Risø International Symposium on Materials Science: Microstructural variability: Processing, analysis, mechanisms and properties : 5–9 September 2022, Department of Civil and Mechanical Engineering, Technical University of Denmark, Denmark - 5–9 September 2022, Department of Civil and Mechanical Engineering, Technical University of Denmark, Denmark. - : IOP Publishing. - 1757-899X. ; 1249
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Konferensbidrag (refereegranskat)abstract
- Harmonic-structure (HS) design is one of the most efficient in the family of architected gradient-structure materials recently attracting increasing attention in global material science community due to leading structural performance characteristics. This work studies in situ the mechanics of plastic deformation in HS materials on the example of commercially pure nickel (Ni) during uniaxial tensile loading. It reveals that strain partitioning between ultrafine and coarse grain fractions in HS Ni commences already at early stages of plastic deformation. Slow accumulation of strain in the ultrafine-grain regions leads to the slow consumption of ductility resource, while accelerated accumulation of strain in the coarse-grain regions leads to an accelerated strain hardening. These effects combined with evolving variations of strain tensor components have synergetic effect leading to the unique plastic behaviour and excellent structural performance of HS materials.
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| 3. |
- Orlov, Dmytro, et al.
(författare)
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Advantages of architectured harmonic structure in structural performance
- 2019
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Ingår i: IOP Conference Series: Materials Science and Engineering. - 1757-8981. ; 580
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Konferensbidrag (refereegranskat)abstract
- The concept of heterogenous materials with architectured harmonic structure (HS) has emerged recently with the aim of enhancing the structural performance of metals. This work presents critical microstructure characteristics contributing to the superior structural performance of harmonic-structured materials using as an example of commercially-pure nickel. Optical and scanning electron microscopy, along with nano-indentation and tensile testing, as well as digital image correlation analysis, were used for this purpose. A brief overview of the structural performance of several representative systems with HS is provided and interesting directions for future studies are discussed.
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| 4. |
- Orlov, Dmytro, et al.
(författare)
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Critical Assesment 37: Harmonic-structure materials - idea, status and perspectives
- 2020
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Ingår i: Materials Science and Technology. - : Informa UK Limited. - 0267-0836 .- 1743-2847. ; 36:5, s. 517-526
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Tidskriftsartikel (refereegranskat)abstract
- Recent efforts in engineering metals with high structural efficiency have resulted in developing a new category of artificial materials with heterogeneous microstructures architected across multiple scales. In this critical assessment, a relatively new concept of heterogeneous bimodal harmonic-structure (bHS) materials is introduced and analysed. It is shown that the bHS concept is applicable to a large variety of metallic materials and is most efficient in scenarios where changes in the chemical composition of materials are restricted for some reason. Basic principles, weaknesses and advantages along with present development status and perspectives are discussed. The overview of critical performance characteristics of various bHS materials is provided, and interesting directions for future research, development and applications are proposed.
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| 5. |
- Orlov, Dmitry, et al.
(författare)
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Obtaining copper with harmonic structure for the optimal balance of structure-performance relationship
- 2013
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Ingår i: Materials Transactions. - 1345-9678. ; 54:9, s. 1549-1553
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Tidskriftsartikel (refereegranskat)abstract
- Materials having bimodal grain structures are known for the good balance of strength and ductility. However, methods for their fabrication often lack the control of such structure characteristics. In this work, the principles of "harmonic" structure fabrication allowing to control both topology and scale of the bimodal structure heterogeneity have been concisely formulated. The feasibility to form the "harmonic structure" in pure copper has been demonstrated, and the advantages of tensile performance of the material with such a structure is analyzed.
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| 6. |
- Sjögren, Elis, et al.
(författare)
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Separation of XRD peak profiles in single-phase metals with bimodal grain structure to analyze stress partitioning
- 2022
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Ingår i: 42nd Risø International Symposium on Materials Science: Microstructural variability: Processing, analysis, mechanisms and properties : 5–9 September 2022, Department of Civil and Mechanical Engineering, Technical University of Denmark, Denmark - 5–9 September 2022, Department of Civil and Mechanical Engineering, Technical University of Denmark, Denmark. - : IOP Publishing. - 1757-899X. ; 1249
-
Konferensbidrag (refereegranskat)abstract
- Materials with bimodal grain size distributions have an attractive combination of strength and ductility. Harmonic structure materials are a category of bimodal-structure materials with a specific microstructure design. The deformation mechanisms of such novel materials during the early stages of deformation are not well understood. Thus, we deformed nickel with harmonic structure in tension until a true strain of 0.04 while recording powder diffraction patterns with high-energy synchrotron X-rays. Line profile analysis based on such data enables quantification of stress states and lattice defect densities in different phases in multi-phase materials. Bimodal size distributions in single-phase materials add extra complexity due to the absence of differences in composition and crystal structure causing the diffraction peaks from fine and coarse grains to appear at the same diffraction angles. Therefore, prior to any meaningful line profile analysis, the respective diffraction profiles need to be separated. A general method for automatically separating profiles originating from different grain fractions in bimodal materials is presented in this work.
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| 7. |
- Sjögren-Levin, Elis, et al.
(författare)
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Grain-level mechanism of plastic deformation in harmonic structure materials revealed by high resolution X-ray diffraction
- 2024
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Ingår i: Acta Materialia. - 1359-6454. ; 265
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Tidskriftsartikel (refereegranskat)abstract
- Materials with heterogeneous microstructures have been reported to have an attractive combination of strength and ductility. This is attributed to synergistic strengthening effects from the difference in strength of fine- and coarse-grained regions. Understanding the interaction of the regions is crucial for further optimization of the microstructures. In this work, we fabricated nickel of harmonic structure (HS) and a reference with homogenous coarse grains. The HS constitutes of an interconnected fine-grained network that surrounds regions of coarse grains. The interplay of the regions was studied by monitoring Bragg reflections from individual grains in situ during tensile deformation until approximately 2 % strain through synchrotron X-ray diffraction. The technique allows grain-level assessment of the degree of plastic deformation. Two grains were followed in the reference and two small grains (fine-grained region) and two large grains (coarse-grained region) in the HS. Three deformation regimes were identified: elastic deformation, onset of plastic deformation and significant plastic deformation. Our results reveal that the large grains in the harmonic structure onset plastic deformation during the macroscopic elastic stage. With increasing applied stress, the small grains yield plastically also and once a large fraction of the fine-grained network deforms plastically the large grains undergo significant plastic deformation. Notably, the onset of significant plastic deformation of large grains in the HS occurs at approximately 100 MPa higher applied stress than in the grains in the reference. This shows that fine grains constrain the large grains from deforming plastically in the HS.
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| 8. |
- Sjögren-Levin, Elis, et al.
(författare)
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Stress partitioning in harmonic structure materials at the early stages of tensile loading studied in situ by synchrotron X-ray diffraction
- 2023
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Ingår i: Scripta Materialia. - : Elsevier BV. - 1359-6462. ; 226
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Tidskriftsartikel (refereegranskat)abstract
- In situ X-ray diffraction was employed to gain insight into the tensile deformation behavior of harmonic structure (HS) nickel. HS consists of a continuous network of fine grains encompassing islands of coarse grains. With the aid of a newly developed separation algorithm, the X-ray diffraction signals from coarse and fine grains were analyzed separately. Using line profile analysis, the evolution of local stresses and microstrains in the respective grain fractions were examined. Several stages were identified during yielding and the onset of plastic deformation in HS nickel. The mechanical behavior of the individual fractions was related to the macroscopic behavior of the HS and compared to that of homogeneous counterparts with similar average grain sizes as the grain fractions. The analysis reveals that the stress partitions between the grain fractions and that the plastic deformation of coarse grains within the HS are constrained by the network of fine grains.
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