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- Ahrentorp, Fredrik, et al.
(författare)
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Sensitive magnetic biodetection using magnetic multi-core nanoparticles and RCA coils
- 2017
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 427, s. 14-18
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Tidskriftsartikel (refereegranskat)abstract
- We use functionalized iron oxide magnetic multi-core particles of 100 nm in size (hydrodynamic particle diameter) and AC susceptometry (ACS) methods to measure the binding reactions between the magnetic nanoparticles (MNPs) and bio-analyte products produced from DNA segments using the rolling circle amplification (RCA) method. We use sensitive induction detection techniques in order to measure the ACS response. The DNA is amplified via RCA to generate RCA coils with a specific size that is dependent on the amplification time. After about 75 min of amplification we obtain an average RCA coil diameter of about 1 mu m. We determine a theoretical limit of detection (LOD) in the range of 11 attomole (corresponding to an analyte concentration of 55 fM for a sample volume of 200 mu L) from the ACS dynamic response after the MNPs have bound to the RCA coils and the measured ACS readout noise. We also discuss further possible improvements of the LOD.
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- Eriksson, Emil, 1990
(författare)
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Dynamic and meta-dynamic recrystallization of Ni-based superalloy Haynes 282
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thermomechanical processes are a crucial manufacturing step because they can “reset” the microstructure, and set the starting point for all following steps. In turn, the microstructure can be used to tailor the mechanical properties of the material. It is therefore of great importance to understand how deformation parameters affect the resulting microstructure. The mechanism responsible for this “reset” of microstructures is recrystallization, where the thermal energy and internal stored energy drive the creation of new, deformation-free, grains at the expense of the deformed ones. However, recrystallization is a complex phenomenon affected by alloy composition, temperature, strain, strain rate etc. In the work presented here, the dynamic, and meta-dynamic recrystallization mechanisms occurring in Ni-base superalloy Haynes 282 are investigated, both below and above the secondary carbide solvus temperature (1100 \C) at various strains, strain rates and post-deformation holding times. Discontinuous dynamic recrystallization, with a clear nucleation of grains at grain boundaries, was observed to be the dominating recrystallization mechanism. For strains up to 0.8 the increase in recrystallized fractions stemmed from nucleation of new grains, whereas for larger strains continued increase in recrystallized fractions was caused by grain growth. Particle stimulated nucleation, where MC carbides acted as nucleation sites, was also observed. Carbides located at grain boundaries did not affect the recrystallization progression significantly. During deformation, the strain rate was seen as the governing factor on the final microstructure, while temperature, strain and holding times were the dominating parameters affecting the meta-dynamic recrystallization. Larger strains led to shorter times to reach a fully recrystallized microstructure during a post-deformation hold. The average grain size also decreased with higher strains applied prior to a static hold.
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- Eriksson, Emil, 1990, et al.
(författare)
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Dynamic and Post-Dynamic Recrystallization of Haynes 282 below the Secondary Carbide Solvus
- 2021
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 11:1, s. 1-24
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Tidskriftsartikel (refereegranskat)abstract
- Thermomechanical processes, such as forging, are important steps during manufacturing of superalloy components. The microstructural development during processing, which controls the final component properties, is complex and depends on e.g., applied strain, strain rate and temperature. In this study, we investigate the effect of process parameters on the dynamic and post-dynamic recrystallization during hot compression of Ni-base superalloy Haynes 282. Specifically, we address the effect of deformation below the grain boundary carbide solvus temperature. During deformation, discontinuous and continuous dynamic recrystallization was observed at the grain boundaries, and particle-stimulated nucleation occurred at primary carbides. Strain rate was determined to be the governing factor controlling the recrystallization fraction for strain rates up to 0.5 s−1 above which adiabatic heating became the dominating factor. Careful examination of the temperature development during deformation showed that the response of the closed-loop temperature control system to adiabatic heating can have important effects on the interpretation of the observed behavior. During a 90 s post-deformation hold, grain growth and an increasing fraction of twin boundaries significantly changed the deformation-induced microstructure and texture. The microstructure developed during post-dynamic recrystallization was mainly controlled by the temperature and only weakly coupled to the prior deformation step.
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| 7. |
- Eriksson, Emil, 1990, et al.
(författare)
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Dynamic recrystallization during hot compression of Ni-based superalloy Haynes 282
- 2023
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Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 960, s. 170837-170837
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the microstructural behaviour of materials during thermomechanical processing is a vital step towards optimizing the mechanical properties. One important aspect during forming processes, such as forging, is dynamic recrystallization (DRX), which sets the starting microstructure for the subsequent manufacturing steps. Here we investigated the DRX behaviour of Ni-base superalloy Haynes 282 during hot compression with a strain rate of 0.05 s−1 at 1080 °C, with care taken to minimize the effects of meta-dynamic recrystallization (mDRX) and adiabatic heating. Small DRX grains could be observed already at ε = 0.1, i.e. before the peak strain εp = 0.15. The DRX process accelerated significantly above ε = 0.2, and the material was fully recrystallized at ε = 1.5. Up to ε = 0.8 DRX occurred through continuous nucleation of new grains, whereas above ε = 0.8 the number density of DRX grains decreased and the increase in recrystallized fraction was due to growth of existing grains. Contrary to common assumptions of DRX nuclei being essentially dislocation free, many of the DRX grains contained pronounced dislocation substructures, even at small strains where they are not expected to have undergone deformation.
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- Eriksson, Emil, 1990, et al.
(författare)
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Meta-Dynamic Recrystallization in the Ni-Based Superalloy Haynes 282
- 2023
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Ingår i: Metals. - : MDPI. - 2075-4701. ; 13:8
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Tidskriftsartikel (refereegranskat)abstract
- Forging on an industrial scale often involves slow, size-limited cooling rates or high temperature hold times between, or after, deformation. This enables the dynamic recrystallization (DRX) initiated during forging to further progress under static conditions, a phenomenon called meta-dynamic recrystallization (mDRX). As mDRX will influence the final grain size, and thus properties, it is critical to understand and control it during processing. Here, we study the mDRX evolution in Ni-based superalloy Haynes 282 during post-deformation hold times of up to 120 s at 1080 °C after partial DRX. We find that mDRX is the dominating mechanisms responsible for the microstructure evolution the hold time. The very rapid mDRX kinetics in the initial stages suggest that quench delays (the time between the end of the deformation and the onset of the quenching intended to arrest the microstructure evolution) must be kept well below 1 s in order to allow reliable conclusions to be drawn from post-deformation microstructure investigations. A larger prior strain (larger DRX fraction) leads to faster mDRX kinetics and a larger final grain size. Larger strains leads to earlier impingement of the growing grains, which, in combination with smaller remaining deformed regions into which the grains can grow, limits the maximum size of the mDRX grains. We also note a close correlation between static recovery and stress relaxation during the hold time, whereas no such correlation between mDRX and stress relaxation can be observed.
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| 9. |
- Eriksson, Emil, 1990
(författare)
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Microstructural evolution during hot compression of a Ni-base superalloy: Dynamic and post-dynamic recrystallization below the secondary carbide solvus temperature
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With an increased demand to lower emissions, the eciency of aircraft engines have to be improved. One way to achieve this is to increase the operation temperature. However, due to the extremely challenging environments in the hot sections of these engines, the current alloys are at their limits. Today, Ni-base superalloys are the materials used for these sections, given their outstanding ability to maintain their strength at temperatures up to 0.8 of their melting temperature, as well as showing excellent corrosion and oxidation resistances. New Ni-base superalloys are developed for these challenges and one of them, Haynes 282, is the alloy investigated in this thesis. In order to tailor an alloys mechanical properties to best suit the needs, the microstructure has be to be processed. The initial working steps for wrought superalloys is forging, which sets the base of the microstructure of all subsequent processing steps. An understanding of how the forging parameters will aect the microstructure is therefore crucial. The dynamic recrystallization mechanisms of the Ni-base superalloy Haynes 282 during hot deformation in a Gleeble were rst investigated. Temperatures both below and above the carbide solvus temperature were studied in order to determine how these parameters aect the resulting microstructure. The microstructures were investigated using electron backscattered diraction and electron channelling contrast imaging in scanning electron microscopes. In order to simulate industrial conditions, samples were held at temperature after deformation in order to evaluate the post dynamic recrystallization phenomena occurring in the Ni-base superalloy for each temperature and strain rate investigated. The microstructures from samples with and without post-deformation hold were compared. An investigation regarding the role of secondary carbides present at grain boundaries during deformation below carbide solvus was also performed, showing that secondary carbides do not aect the recrystallization signicantly. Parameters like temperature and strain rate have a larger impact.
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| 10. |
- Eriksson, Emil, 1990, et al.
(författare)
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The Effect of Grain Boundary Carbides on Dynamic Recrystallization During Hot Compression of Ni-Based Superalloy Haynes 282
- 2022
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Ingår i: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. - : Springer Science and Business Media LLC. - 1073-5623. ; 53:1, s. 29-38
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Tidskriftsartikel (refereegranskat)abstract
- In alloys where carbides are the main grain boundary phase, the role of carbides during hot working is not known. Here, we address the effect of grain boundary carbides on the dynamic recrystallization during hot compression of Ni-base superalloy Haynes 282. When excluding variations from experimental factors neither stress evolution nor final microstructure indicated that carbides exerted a significant influence on the dynamic recrystallization. The carbide solvus temperature is not a critical limit during thermomechanical processes.
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