| 1. |
- Jensen, D. Juul, et al.
(författare)
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Importance of local structural variations on recrystallization
- 2013
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Ingår i: Material Science Forum. - : Trans Tech Publications Inc.. - 9783037856888 ; , s. 37-41
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Konferensbidrag (refereegranskat)abstract
- Effects of local variations in the deformation microstructure on subsequent recrystallization are discussed and illustrated by three examples. The three examples consider local variations on different length scales and are: 1. Effects of local variations in the deformation microstructure on the formation of protrusions on migrating boundaries. 2. Effects of an inhomogeneous spatial distribution of second phase particles on growth. 3. Effects of stored energy and orientation variations on recrystallization kinetics.
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| 2. |
- Kattge, Jens, et al.
(författare)
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TRY plant trait database - enhanced coverage and open access
- 2020
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Ingår i: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 26:1, s. 119-188
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Tidskriftsartikel (refereegranskat)abstract
- Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
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| 3. |
- Lin, Fengxiang, et al.
(författare)
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Comment : On the nature of “unconventional twins” in magnesium
- 2023
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Ingår i: Scripta Materialia. - : Acta Materialia Inc. - 1359-6462 .- 1872-8456. ; 224
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Tidskriftsartikel (refereegranskat)abstract
- “Unconventional twins” were reported by Cayron and Logé [1] to form in plastically deformed magnesium. They were used to show the occurrence of a new twinning mode which was used to argue for reconsidering the theory of deformation twinning that is based on simple shear [1], and to support a concept of axial weak twins [2]. Our paper demonstrates the incorrect interpretation of their electron back-scatter diffraction map in [1], and that the so-called “unconventional” twins are just conventional extension twins that have impinged with each other. Therefore, the so-called habit plane of the “unconventional twins” is a boundary resulting from impingement of these two different variants of the extension twin, and is therefore not expected to be invariant. © 2022 Acta Materialia Inc.
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| 4. |
- Lin, Fengxiang, et al.
(författare)
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Effects of structural heterogeneity of nanostructured copper on the evolution of the sizes of recrystallized grains during annealing
- 2015
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Ingår i: IOP Conference Series. - : Institute of Physics (IOP).
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Konferensbidrag (refereegranskat)abstract
- Recrystallization in copper deformed by dynamic plastic deformation was investigated using electron backscatter diffraction. The recrystallized grains show a broad size distribution. The kinetics of grains of different sizes is observed to be different: In the beginning of recrystallization, the area fraction of small recrystallized grains increases rapidly. At later stages of recrystallization, the area fraction of small recrystallized grains is stable, while the area fractions of medium and large recrystallized grains increase. Correlation between the broad grain size distribution (and its evolution) and the heterogeneous deformed microstructure is discussed. © Published under licence by IOP Publishing Ltd.
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| 5. |
- Lin, Fengxiang, et al.
(författare)
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Importance of Non-uniform Boundary Migration for Recrystallization Kinetics
- 2018
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940. ; 49:11, s. 5246-5258
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Tidskriftsartikel (refereegranskat)abstract
- Recrystallization kinetics is studied by three characterization methods: post-mortem electron microscopy, in situ three-dimensional X-ray diffraction (3DXRD), and ex situ electron microscopy. Cold-rolled copper is used as a model material. The post-mortem analysis shows that the average migration velocity of unimpinged recrystallizing boundaries decreases strongly with annealing time, leading to a low Avrami exponent. For individual grains, the in situ 3DXRD measurement reveals that the growth rates decrease significantly shortly after nucleation. This is explained by the ex situ characterizations, which show that different segments of the recrystallizing boundaries migrate with significantly different velocities, and some boundaries, although unimpinged, remain stationary. This non-uniform migration of recrystallizing boundaries leads to an amoeba-like growth, and is proposed to be responsible for the decrease of the average boundary migration velocity, because the fraction of slowly moving/stationary boundaries increases during the recrystallization. Reasons for stationary boundaries are discussed based on a quantitative analysis of the local deformed microstructure. It is concluded that non-uniform boundary migration has a significant influence on recrystallization kinetics and needs to be included in recrystallization models. © 2018, The Minerals, Metals & Materials Society and ASM International.
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| 6. |
- Lin, Fengxiang, et al.
(författare)
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Local strain distributions in partially recrystallized copper determined by in situ tensile investigation
- 2015
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Ingår i: IOP Conference Series. - : Institute of Physics Publishing (IOPP).
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Konferensbidrag (refereegranskat)abstract
- A partially recrystallized copper sample produced by cold-rolling and annealing was deformed in situ by uniaxial tension in a scanning electron microscope, and electron backscatter diffraction data were collected before and after deformation to certain strains. The local strain distributions are quantified using digital image correlation. Distributions of the normal strain along the tensile direction (εxx) are shown in this paper. The recrystallized grains are found to deform more than the remaining unrecrystallized matrix. When εxx is averaged along lines perpendicular to the tensile direction, significant variation are observed, which may be related to the local recrystallized volume fraction. © Published under licence by IOP Publishing Ltd.
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| 7. |
- Lin, Fengxiang, et al.
(författare)
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Supercube grains leading to a strong cube texture and a broad grain size distribution after recrystallization
- 2015
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Ingår i: Philosophical Magazine. - : Taylor & Francis. - 1478-6435 .- 1478-6443. ; 95:22, s. 2427-2449
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Tidskriftsartikel (refereegranskat)abstract
- This work revisits the classical subject of recrystallization of cold-rolled copper. Two characterization techniques are combined: three-dimensional X-ray diffraction using synchrotron X-rays, which is used to measure the growth kinetics of individual grains in situ, and electron backscatter diffraction, which is used for statistical analysis of the microstructural evolution. As the most striking result, the strong cube texture after recrystallization is found to be related to a few super large cube grains, which were named supercube grains. These few supercube grains become large due to higher growth rates. However, most other cube grains do not grow preferentially. Because of the few supercube grains, the grain size distribution after recrystallization is broad. Reasons for the higher growth rates of supercube grains are discussed, and are related to the local deformed microstructure. © 2015 Taylor & Francis.
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| 8. |
- Liu, H., et al.
(författare)
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Formation and autocatalytic nucleation of co-zone {101¯2} deformation twins in polycrystalline Mg : A phase field simulation study
- 2018
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Ingår i: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 153, s. 86-107
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Tidskriftsartikel (refereegranskat)abstract
- A phase-field model is developed to study the formation and autocatalytic nucleation of {101¯2} twins in polycrystalline Mg. The twins are found to nucleate most favourably in grains with the most negative interaction energy. Within such grains, the energetically most favoured nucleation site is determined by stresses concentrated near the grain boundaries that are related to the elastic anisotropy of the material. Furthermore, in a structure consisting of three lamellar grains with an incoming twin in the central grain, the simulation results show that before autocatalytic nucleation, the incoming twin often has a lenticular shape. The stress field around the tip of the incoming twin plays the major role in the autocatalytic nucleation. After a twin has nucleated in the neighbouring grain, the incoming and the outgoing twins evolve simultaneously, and the shape of the incoming twin gradually changes from lenticular to parallel-sided plate. Under the condition that the crystallographic orientation of the central grain and the applied strain remains unchanged, the driving force for twin nucleation decreases with increasing misorientation (up to 90°) across the grain boundary. It is further derived that the interaction energy values between the pre-existing stress field of the polycrystalline structure and the eigenstrain of the to-be-nucleated twin is mathematically related to the resolved shear stress of twins. © 2018 Acta Materialia Inc.
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| 9. |
- Xu, C., et al.
(författare)
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Crystallographic Analysis of Nucleation at Hardness Indentations in High-Purity Aluminum
- 2016
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer. - 1073-5623 .- 1543-1940. ; 47:12, s. 5863-5870
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Tidskriftsartikel (refereegranskat)abstract
- Nucleation at Vickers hardness indentations has been studied in high-purity aluminum cold-rolled 12 pct. Electron channeling contrast was used to measure the size of the indentations and to detect nuclei, while electron backscattering diffraction was used to determine crystallographic orientations. It is found that indentations are preferential nucleation sites. The crystallographic orientations of the deformed grains affect the hardness and the nucleation potentials at the indentations. Higher hardness gives increased nucleation probabilities. Orientation relationships between nuclei developed at different indentations within one original grain are analyzed and it is found that the orientation distribution of the nuclei is far from random. It is suggested that it relates to the orientations present near the indentation tips which in turn depend on the orientation of the selected grain in which they form. Finally, possible nucleation mechanisms are briefly discussed. © 2016, The Minerals, Metals & Materials Society and ASM International.
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| 10. |
- Xu, C L, et al.
(författare)
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Impact of local Si segregation on strain localization in ductile cast iron
- 2020
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Ingår i: IOP Conference Series: Materials Science and Engineering. - : Institute of Physics Publishing (IOPP).
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Konferensbidrag (refereegranskat)abstract
- The distribution of Si content in tensile deformed ductile cast iron has been characterized using electron microscopy and correlated to the strain distribution determined based on 3D tomography data collected before and after tensile deformation and digital volume correlation analysis. The results show that the high plastic strain regions localize in bands consisting of large graphite nodules and deformed matrix with high Si content connecting the graphite nodules in the first-to-solidify regions. The bands are aligned about 45° with respect to the loading direction, which is close to the maximum shear direction.
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