| 1. |
- Almer, J., et al.
(författare)
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Strain and texture analysis of coatings using high-energy x-rays
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 94:1, s. 697-702
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the internal strain and crystallographic orientation (texture) in physical-vapor deposited metal nitride coatings of TiN and CrN. A high-energy diffraction technique is presented that uses synchrotron x rays and an area detector, and which allows the strain and intensity distributions of multiple crystallographic planes to be measured by a single x-ray exposure. Unique texture states and nonlinear sin2 strain distributions are observed for all coatings investigated. Quantitative analysis indicates that existing micromechanical models can reasonably predict strain and corresponding stress for mixed-hkl reflections but are inadequate for fully describing measured data. Alternative mechanisms involving deposition-induced defects are proposed
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| 2. |
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| 3. |
- Hedström, Peter, et al.
(författare)
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Load partitioning and strain-induced martensite formation during tensile loading of a metastable austenitic stainless steel
- 2009
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940. ; 40:5, s. 1039-1048
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Tidskriftsartikel (refereegranskat)abstract
- In-situ high-energy X-ray diffraction and material modeling are used to investigate the strain-rate dependence of the strain-induced martensitic transformation and the stress partitioning between austenite and α′ martensite in a metastable austenitic stainless steel during tensile loading. Moderate changes of the strain rate alter the strain-induced martensitic transformation, with a significantly lower α′ martensite fraction observed at fracture for a strain rate of 10−2 s−1, as compared to 10−3 s−1. This strain-rate sensitivity is attributed to the adiabatic heating of the samples and is found to be well predicted by the combination of an extended Olson–Cohen strain-induced martensite model and finite-element simulations for the evolving temperature distribution in the samples. In addition, the strain-rate sensitivity affects the deformation behavior of the steel. The α′ martensite transformation at high strains provides local strengthening and extends the time to neck formation. This reinforcement is witnessed by a load transfer from austenite to α′ martensite during loading.
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| 4. |
- Hegedüs, Z., et al.
(författare)
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Imaging modalities at the Swedish Materials Science beamline at PETRA III
- 2019
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Ingår i: IOP Conference Series. - : Institute of Physics Publishing.
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Konferensbidrag (refereegranskat)abstract
- High-energy synchrotron radiation has been demonstrated to be a powerful tool for materials characterization. The development of novel methodologies is still ongoing, driven by major technological advances regarding the available source brilliance and efficient large area detectors. The Swedish Materials Science beamline at PETRA III is dedicated to materials characterization by high-energy X-rays and scheduled to enter into user operation starting August 2019. The beamline has been designed in particular for the combination of two complementary techniques: wide and small angle scattering and imaging. The beamline design is presented briefly and the different techniques are reviewed with regard to the contrast mechanisms and the ability to obtain spatially resolved information.
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| 5. |
- Jiang, S., et al.
(författare)
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Micromechanical behavior of multilayered Ti/Nb composites processed by accumulative roll bonding : An in-situ synchrotron X-ray diffraction investigation
- 2021
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Ingår i: Acta Materialia. - Oxford, United Kingdom : Elsevier. - 1359-6454 .- 1873-2453. ; 205
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Tidskriftsartikel (refereegranskat)abstract
- Heterophase interfaces play a crucial role in deformation microstructures and thus govern mechanical properties of multilayered composites. Here, we fabricated Ti/Nb multilayers by accumulative roll bonding (ARB) where shear bands became predominant with increasing rolling cycles. To explore correlation between micromechanical behavior and mechanical properties of the composites with various lamellar morphologies, in-situ high-energy X-ray diffraction tensile tests were performed. The results quantitatively reveal that the rapid strengthening of the composites with increasing ARB cycles mainly originates from the Nb layers strengthened by dislocations, grain boundaries and heterophase interfaces, and the {211} grains mostly contribute to the global strain hardening. The softer Ti grains also extend global strain hardening to a wide range and postpone necking. Furthermore, complete stress state analysis show that in the presence of extensive shear bands, significant load partitioning between the neighboring metals leads to triaxial stresses in each constituent and dislocations tend to slip along the shear direction. This promotes dislocation multiplication and motion, which is conducive to overall strength enhancement while maintaining a satisfactory ductility. These findings elucidate the effect of strong constraints of the interfaces on mechanical properties, which provides a fundamental understanding of load partitioning and strengthening mechanisms of the multilayers processed by multiple ARB cycles.
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| 6. |
- Tian, Ye, et al.
(författare)
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Micromechanics and microstructure evolution during in situ uniaxial tensile loading of TRIP-assisted duplex stainless steels
- 2018
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Ingår i: Materials Science & Engineering. - : Elsevier Ltd. - 0921-5093 .- 1873-4936. ; 734, s. 281-290
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Tidskriftsartikel (refereegranskat)abstract
- Transformation-induced plasticity (TRIP) assisted duplex stainless steels, with three different stabilities of the austenite phase, were investigated by synchrotron x-ray diffraction characterization during in situ uniaxial tensile loading. The micromechanics and the deformation-induced martensitic transformation (DIMT) in the bulk of the steels were investigated in situ. Furthermore, scanning electron microscopy supplemented the in situ analysis by providing information about the microstructure of annealed and deformed specimens. The dependence of deformation structure on austenite stability is similar to that of single-phase austenitic steels with shear bands and bcc-martensite (α′) generally observed, and blocky α′ is only frequent when the austenite stability is low. These microstructural features, i.e. defect structure and deformation-induced martensite, are correlated with the micro- and macro-mechanics of the steels with elastoplastic load transfer from the weaker phases to the stronger α′, in particular this occurs close to the point of maximum rate of α′ formation. A clear strain-hardening effect from α′ is seen in the most unstable austenite leading to a pronounced TRIP effect.
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