| 1. |
- Lissel, Linda, et al.
(author)
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Prediction of the microstructural evolution during hot strip rolling of Nb microalloyed steels
- 2007
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In: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 558-559:2, s. 1127-1132
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Conference paper (other academic/artistic)abstract
- A physically based model is used to describe the microstructural evolution of Nb microalloyed steels during hot rolling. The model is based on a physical description of dislocation density evolution, where the generation and recovery of dislocations determines the flow stress and also the driving force for recrystallization. In the model, abnormally growing subgrains are assumed to be the nuclei of recrystallized grains and recrystallization starts when the subgrains reach a critical size and configuration. The model is used to predict the flow stress during rolling in SSAB Tunnplat's hot strip mill. The predicted flow stress in each stand was compared to the stresses calculated by a friction-hill roll-force model. Good fit is obtained between the predicted values by the microstructure model and the measured mill data, with an agreement generally within the interval +/-15%.
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| 2. |
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| 3. |
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| 4. |
- Hutchinson, Bevis
(author)
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Origin of goss texture during secondary recrystallisation in silicon-steel
- 2012
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Conference paper (peer-reviewed)abstract
- Primary recrystallised sheets of 3% silicon steel from two different industrial processing routes have been examined after laboratory annealing to initiate secondary recrystallisation. Metallography included etching to reveal individual dislocations and sub-boundaries as well as EBSD in scanning electron microscopy. Residual low angle boundaries are not normally observed inside the secondary grains. The growth of secondaries appears to occur in a jerky manner, associated with local intrusions into the primary matrix that destabilise the interface. The frequency of occurrence of special low energy grain boundaries such as ∑9 and ∑5 is believed to dictate the selectivity of the Goss orientation in both types of steel sheet. © (2012) Trans Tech Publications, Switzerland.
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| 5. |
- Kaiser, M., et al.
(author)
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Polycrystalline SiC as source material for the growth of fluorescent SiC layers
- 2013
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In: Silicon Carbide And Related Materials 2012. - : Trans Tech Publications Inc.. - 9783037856246 ; , s. 39-42
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Conference paper (peer-reviewed)abstract
- Polycrystalline doped SiC act as source for fluorescent SiC. We have studied the growth of individual grains with different polytypes in the source material. We show an evolution and orientation of grains of different polytypes in polycrystalline SiC ingots grown by the Physical Vapor Transport method. The grain influence on the growth rate of fluorescent SiC layers grown by a sublimation epitaxial process is discussed in respect of surface kinetics.
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| 6. |
- Karlsson, Oskar
(author)
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Ageing of brazed aluminium AA6xxx alloys for vehicle radiators
- 2014
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Conference paper (peer-reviewed)abstract
- Some aluminium alloys with Mg-Si age-hardening are used in vehicle radiators. For cost reasons they are preferably delivered in a naturally aged temper. Estimated minimum time of natural ageing between brazing and when the radiator is taken into service is 14 days. At the service temperature of 95°C, the radiator material will continue to age harden. For accelerated durability testing it is vital to use a radiator with the strength and ageing response of a service radiator. We investigated whether the full 14 days of natural ageing were needed, or if the time could be shortened. Since a vehicle is not in constant use, the radiator temperature will vary over time. We therefore compared cyclic ageing between ambient temperature and 95°C to continuous ageing at 95°C. The Gränges alloys FA7870 (for headers) and FA7850 (for tubes) were subjected to different ageing times at different temperatures. Tensile and hardness were tests performed to assess the ageing effect. It was found that natural ageing reduced hardening during the subsequent ageing at service temperature, an effect that was most pronounced for the first four days. There was no difference between continuous and cyclic ageing. © (2014) Trans Tech Publications, Switzerland.
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| 7. |
- Linnarsson, Margareta K., et al.
(author)
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Lateral boron distribution in polycrystalline sic source materials
- 2013
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In: Silicon Carbide And Related Materials 2012. - : Trans Tech Publications Inc.. - 9783037856246 ; , s. 397-400
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Conference paper (peer-reviewed)abstract
- Polycrystalline SiC containing boron and nitrogen are used in growth of fluorescent SiC for white LEDs. Two types of doped polycrystalline SiC have been studied in detail with secondary ion mass spectrometry: sintered SiC and poly-SiC prepared by sublimation in a physical vapor transport setup. The materials are co-doped materials with nitrogen and boron to a concentration of 1x1018 cm-3 and 1x1019 cm-3, respectively. Depth profiles as well as ion images have been recorded. According to ocular inspection, the analyzed poly-SiC consists mainly of 4H-SiC and 6H-SiC grains. In these grains, the boron concentration is higher and the nitrogen concentration is lower in the 6H-SiC compared to the 4H-SiC polytype. No inter-diffusion between grains is observed.
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| 8. |
- Martin, David, et al.
(author)
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Dilatometer analysis of the one step quenching and partitioning process in a 1.5%Si steel
- 2014
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Conference paper (peer-reviewed)abstract
- A one step quenching and partitioning process was applied to a 0.2%C-2.0%Mn-0.5%Cr- 1.5%Si steel by quenching austenitised samples to several different temperatures below the experimentally determined martensite start temperature of 397 °C and isothermally partitioning them before quenching to room temperature using a quenching deformation dilatometer. These treatments yielded predominantly martensitic microstructures containing 5:6 vol.% to 7:5 vol.% retained austenite, as measured by x-ray diffraction. In each treatment, strong dilation was recorded during isothermal partitioning, with little indication of phase transformation during subsequent cooling to room temperature. This behaviour lends weight to the idea that an isothermal phase transformation occurred during partitioning, and that the final microstructure is a mixture of athermally and isothermally formed constituents. These results also suggest that the final microstructure of this steel is mostly formed before and during partitioning. © (2014) Trans Tech Publications, Switzerland.
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| 9. |
- Ou, Y., et al.
(author)
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Fabrication of broadband antireflective sub-wavelength structures on fluorescent SiC
- 2013
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In: Materials Science Forum. - 9783037856246 ; , s. 1024-1027
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Conference paper (peer-reviewed)abstract
- Surface nanocones on 6H-SiC have been developed and demonstrated as an effective method of enhancing the light extraction efficiency from fluorescent SiC layers. The surface reflectance, measured from the opposite direction of light emission, over a broad bandwidth range is significantly suppressed from 20.5% to 1.0% after introducing the sub-wavelength structures. An omnidirectional light harvesting enhancement (>91%), is also achieved which promotes fluorescent SiC as a good candidate of wavelength converter for white light-emitting diodes
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| 10. |
- Sadrossadat, Mohsen, et al.
(author)
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Analysis of residual stress development during thermal processing of Al-Si alloys
- 2010
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Conference paper (peer-reviewed)abstract
- Residuals stresses can be present in almost every industrial component. Manufacturing processes such as casting, welding, and heat treatment are the most common causes of residual stresses. Thermal residual stresses could be developed in a component during heat treatment process as a result of non-uniform heating or cooling operations. In this study, experiments were carried out to develop insights into and understanding of the residual stresses that can arise during thermal treatments of Al-Si components. Due to the complexity of residual stresses analysis in real components, a common mixed-section casting was employed. In order to fulfill the requirements of performing different thermal treatments, a special cooling apparatus was designed and built. A number of the casting components of an Al-Si alloy were annealed for stress relief, and then removed from the furnace and cooled with different water flow rates. Then, the amount of accumulated residual stresses in the components was measured relaxation of stress using cutting. Thermal analysis and residual stress measurement for different thermal treatment regimes showed that by choosing a specific holding temperature before direct cooling, the value of residual stress increases linearly with flow rate of cooling. On the other hand, for a constant value of cooling water flow, ∆Tmax and residual stress level decreases when the value of base temperature of furnace decreases. Moreover, the cutting method can be a suitable method for measuring thermal residual stresses in Al-Si components and thermal analysis is a powerful technique to predict residual stresses.
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| 11. |
- Siwecki, Tadeusz, et al.
(author)
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Optimising thermomechanical processing with reduced energy demand
- 2012
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Conference paper (peer-reviewed)abstract
- Improving the steel properties and production processes with reduced energy demand for high strength steels requires improved process control in close relation to the steel composition. Hot rolling of steel is an energy-intensive process, especially in respect of preheating the steel slabs. The present work was carried out with the aim of reducing the initial slab temperature while at the same time improving properties by optimization of the steel composition and process parameters. Optimization of slab reheating and hot rolling parameters in connection with plate and strip rolling was carried out on low C-Mn high-strength steels microalloyed with Mo-Ti-Nb-B, both in laboratory and full scales processing. The effects of a low slab reheating temperature, high finish rolling temperature (FRT) during thermo-mechanical controlled processing (TMCP) and accelerated cooling rates following hot rolling to RT or to the coiling temperature have been investigated. Improvement of yield strength of the plate has been obtained by lowering the slab reheating temperature, especially with high cooling rates (>20°C/s) to room temperature. The results obtained for strip steels also show that a reduced reheating temperature combined with high finish rolling temperatures and cooling rates (>20°C/s) to a coiling temperature of 450°C produces very positive microstructures and mechanical properties in the present steels. Lowering the slab reheat temperature reduces energy consumption and accordingly releases less CO 2 into the atmosphere during the thermo-mechanical processing of the present steels. © 2012 Trans Tech Publications, Switzerland.
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| 12. |
- Toth-Pal, Zsolt, et al.
(author)
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Pressure dependence of thermal contact resistance between copper heat sink and copper DBC surfaces in SiC power device packages
- 2014
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In: Silicon Carbide and Related Materials 2013. - : Trans Tech Publications Inc.. - 9783038350101 ; , s. 1118-1121
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Conference paper (peer-reviewed)abstract
- Thermal contact resistances have been measured in an experiment emulating heat transfer from a SiC die to a cooled heat sink through a heat spreader and a DBC structure. The major surface-dependent parameters are the surface roughness, surface hardness, and planarity. The measured thermal contact resistances are in agreement with theoretical values. When investigating DBC copper surfaces a second interface between the bonded Cu to AlN has to be taken into account.
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| 13. |
-
Science and Processing of Cast Iron XI
- 2018
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Editorial proceedings (peer-reviewed)abstract
- The goal of this book is to present for readers the articles from the 11th International Symposium on the Science and Processing of Cast Iron that was held in September 2017 in Jönköping, Sweden. The content of the book reflects the state of the art, research and development tendencies of cast iron as the main engineering cast material also in the 21st century.
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| 14. |
- Meng, Y., et al.
(author)
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A study on energy consumption of a CNC milling machine based on cutting force model
- 2014
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Conference paper (peer-reviewed)abstract
- Machining operations are performed by machine tools with a large amount of energy consumed for material removal. Understanding and characterizing the energy consumption is essential to explore the potential of energy-saving in energy-efficient machining. For this purpose, this paper proposes a method for modeling energy consumption of end milling operation which is based on cutting theory. The cutting power model is verified with experiments on a CNC milling machine. According to the calculated and experimental results, it is clear that the theoretical prediction can predict the mean cutting power successfully as validated by actual measurements.
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