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  • 301.
    Svensson, Jennie
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Larsson, F.
    Memarpour, A.
    Ekerot, S.
    Brabie, Voicu
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Jönsson, P.G.
    Implementation of an YSZ coating material to prevent clogging of the submerged entry nozzle (SEN) during continuous casting of Ce-treated steels2018Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 45, nr 2, s. 105-113Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The possibility to reduce clogging in the submerged entry nozzle (SEN) during continuous casting of Ce alloyed stainless steels has been studied. This was done by implementing a new plasma coating material, consisting of yttria stabilized zirconia (YSZ). The coating was first tested in pilot-plant trials; where the amount of steel teemed through the plasma coated nozzles was monitored. Thereafter, samples of the coatings from the nozzles were studied using a FEG-SEM equipped with EDS. In addition, the coating material was tested in industrial trials where the performance was judged with respect to the clogging tendency detected as the movement of the stopper rod. The results from both the pilot-plant trials and industrial trials showed that the use of an YSZ coating led to a decreased clogging tendency during the casting in comparison to when using an uncoated SEN. Specifically, the pilot-plant trials showed that the clogging factor was lowered when implementing the YSZ coatings. Furthermore, the industrial trials showed that the clogging tendency, measured by the stopper rod movements, were lower when implementing the YSZ coating.

  • 302.
    Svensson, Jennie
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Larsson, Fredrik
    Outokumpu, Avesta SE-774 22, Sweden.
    Memarpour, Arashk
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik. Sandvik Materials Technology, Sandviken SE-811 81, Sweden.
    Brabie, Voicu
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Jönsson, Pär
    Royal Institute of Technology, Brinellvägen 23, Stockholm SE-100 44, Sweden.
    Post-mortem Studies of Submerged Entry Nozzles (SEN) Coated with Yttria Stabilized Zirconia (YSZ)2015Ingår i: The 6th International Congress on the Science and Technology of Steelmaking (ICS2015), China, May 12-14, 2015 in Beijing / [ed] Organized by The Chinese Society for Metals (CSM), 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    During continuous casting of Ce-treated stainless steel grades an accumulation of inclusions at the submerged entry nozzle’s (SEN) internal wall can cause disturbances or even prevent the molten steel flow. Plasma sprayed yttria stabilized zirconia (YSZ) coating of the SEN’s inlet and stopper rod have been implemented in order to decrease the clogging effect. The coating thickness was 210 µm and the plant trials were conducted during continuous casting of slabs. The clogging tendency was measured by the stopper rod position during the casting process. The results of the measured positions were then compared to experimentally determined information from samples cut out from the SEN’s inlet after casting. Specifically, the samples were analysed using a field emission gun scanning electron microscope (FEG-SEM) equipped with an energy dispersive X-ray spectrometry (EDS). Sample with the dimensions of ̴15x10x5 mm were electrolytic extracted before analysis. The chemical composition at the interface between the solidified steel and refractory base materials were analysed, and traces of the YSZ coating were determined.

    The movement of the stopper position indicated that the clogging tendency was reduced for the coated SEN. However, the FEG-SEM analyses showed that clogging of the SEN had occurred during the casting.

  • 303.
    Svensson, Jennie
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik. KTH.
    Memarpour, Arashk
    Brabie, Voicu
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik. KTH.
    Jönsson, Pär
    KTH.
    Studies of the decarburisation phenomena during preheating of submerged entry nozzles (SEN) in continuous casting processes2017Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 44, nr 2, s. 108-116Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Decarburisation of the submerged entry nozzles (SEN) during the preheating process wasinvestigated based on plant trials and thermodynamic modelling at three different steel plants.During the trials the preheating processes were mapped, the temperature profiles wereregistered and post-mortem studies of the SENs with scanning electron microscopy wereperformed. Typically, the glass/silicon powder will form a dense and protective layer inside theSEN when heated over 1100°C. However, this study found that the temperature distributioninside the SEN did not always reach this critical temperature. Thus, decarburisation of the SENwas found at all steel plants. The overall results illustrate that the control of the preheatingprocess needs to be improved at all steel plants. It is suggested that future research should befocused on the development of new coating materials to prevent decarburisation of therefractory base material, which would decrease the chances of clogging during casting.

  • 304.
    Svensson, Jennie
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik. KTH, Tillämpad processmetallurgi.
    Memarpour, Arashk
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Brabie, Voicu
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Jönsson, Pär
    KTH, Tillämpad processmetallurgi.
    Studies of the decarburization phenomena during heating of submerged entry nozzles (SEN) in continuous casting processesManuskript (preprint) (Övrigt vetenskapligt)
  • 305.
    Svensson, Jennie
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Memarpour, Arashk
    Ekerot, Sven
    Brabie, Voicu
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Jönsson, Pär
    Tillämpad processmetallurgi, KTH.
    Studies of new coating materials to prevent clogging of the submerged entry nozzle (SEN) during continuous casting of Al killed low carbon steels2017Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 44, nr 2, s. 117-127Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The possibility to reduce clogging in the submerged entry nozzle (SEN) when casting Al killed low carbon steel has been evaluated. The coating materials have been tested in laboratory trials and pilot plant trials. Totally, 2 mixes of the coating material has been tested; containing 4.8 and 9.1 % CaTiO3 mixed with yttria stabilised zirconia (YSZ) powder. The chemical composition was analysed by using an FEG-SEM equipped with EDS.The major result showed that alumina reacted with CaTiO3 in the temperature interval from 1550-1600°C. In addition, the clogging ratio showed a decreased clogging tendency for coated nozzles compared to standard nozzles. Also, the results showed that an approximately three times higher steel mass could be teemed through the coated nozzles before clogging occurred compared to trials with uncoated standard nozzles. Overall, it is concluded that plasma sprayed CaTiO3 coatings can reduce the clogging tendency during the continuous casting process.

  • 306.
    Tahir, Mohammed
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    LOWWEAR varmvalsning WP12012Ingår i: Strategiskt stålforskningsprogram för Sverige 2007–2012: En sammanfattning av forskningsprogrammet och de ingående projekten, presenterade vid Jernkontorets programkonferens, 4–5 september 2012, Stockholm: Jernkontoret , 2012, s. 18-18Konferensbidrag (Övrig (populärvetenskap, debatt, mm))
    Abstract [sv]

    En konstruktion av slitage och temperaturprofiler in-line¬mätare designades och ett modifierat valslitage beräkningsmodell presenteras där inflytandet från arbetsvalsmaterial och det valsade materialets egen-skaper utvärderades. HSS, HiCr och IC arbetsvalsar utvärderades. Olika par i färdigverk med olika valsar-rangemang, skillnader i slitage mellan övre och undre valsar och påverkan av smörjning undersöktes.  Genom att anpassa modellen till olika valsningsförhållanden; varmvalsverk, plåtverk och steckelverk, erhölls möjligheten att undersöka modellen i drift.

    En studie av valsmaterial (Vancron 40, Sverker 3 and Vanadis 23) med avseende på valsslitage, ytkvalitet och påkladdning genomfördes. Valsmaterialen utvärderades experimentellt i laboratorium och i pilotvals-verk. Fyra olika industriella smörjmedel utvärderades. Vancron 40 gav lovande materialkvalitet tack vare sina goda egenskaper gällande ytfinhet i kombination med motstånd mot påkladdning och motstånd mot adhesiv nötning.

  • 307.
    Tahir, Mohammed
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Absalyamova, V.
    The use of solar energy in steel industries2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    The purpose of this study is to make a design and simulation of the solar photovoltaic system which would attempt to cover the energy demand of the initial part of the pickling line hydraulic system at the SSAB steel plant. Proposed photovoltaic pumping systems in this work are to run the system into the hydraulic pump directly, developing of PV systems which produce energy in DC form. The second proposed photovoltaic technology is a type of PV system which delivers power to an AC load. © 2011 IEEE.

  • 308.
    Tahir, Mohammed
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Holmberg, Jesper
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    The impact of tapered work rolls in the finishing mill during hot rolling2012Ingår i: Iron & Steel Technology Conference Proceedings, Warrendale, PA: Association for Iron & Steel Technology , 2012, s. 1601-1609Konferensbidrag (Refereegranskat)
    Abstract [en]

    Few studies were done to assess the knowledge of the impact of tapered work rolls in the finishing mill during hot rolling. Hansson, L.et al. studied the use of advanced process models for plate and strip rolling in the Scandinavian Steel Industry [1]. Their work thatincludes simulations of work roll shift with tapered and CVC rolls have results a basis for new investments for profile and flatnesscontrol equipment in steel rolling mills. Rosenthal D. et al. studied a method of influencing the strip contour in the edge region of arolled strip [2]. Special CVC rolls were used as work rolls for influencing the strip contour in the edge areas and to study.Concerning this project, early analysis of work roll data suggested that the tapering of the work rolls was subordinated to the CVCprofileand that a greater than allowed tapering would not affect the result of the rolling process. A grinded profile which is out oftolerance on the other hand, would result in a change in CVC-profile.The purpose of this project was to study the impact of the tapering on the work rolls during hot rolling in the finishing mill. Customgrinded work rolls of CVC-type have been placed in finishing mill, stand 6 (F6) and the axial loads during the following rolling hasbeen studied and evaluated. The deviation of the centre of a strip, flatness of a strip as well as the equivalent camber of the work rollshave also been analyzed for further evaluations of the impact on the rolling results.Theoretically calculation model of the profile of the CVC work rolls and axial force directed toward roll edges was described. Customgrinded work rolls of CVC-type have been placed in mill stand number 6 and the axial loads during the following rolling has beenstudied and evaluated.The impact of tapered work rolls towards CVC profile, axial force, the deviation of the centre of a strip and flatness was presented.The work project finally resulted in new guidelines in grinding of the work rolls in the finishing mill.The work is done in the finishing mill of the strip rolling mill, Figure 1. The strip rolling mill comprising six-high rolling stands wherework rolls and backup rolls at stand 2 to 6 are containing CVC work rolls.Data of the specific strip rolling mill, the type and the characteristics of the used work rolls and strip properties were described [3].Due to different rolling conditions; high temperature in the early stands (thermal cracks) and low temperature and high incident rate inthe last stands (mechanical damage), HSS and HCr rolls were used in stands F1-F3 and IC rolls in stands F4-F6. The studied work rollwas of IC type.

  • 309.
    Tahir, Mohammed
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Jonsson, N.G.
    Lagergren, J
    Wikström, L.
    Hedenlund, H
    Evaluation of tool material Vancron 40 with regard to wear, surface quality and galling2012Ingår i: Proceedings of  JSI 2012 - 30th International Steel Industry Conference, December 18-19, Paris, France, Paris: B&W , 2012, , s. 2Konferensbidrag (Refereegranskat)
    Abstract [en]

    Resistance to adhesive wear on tool material can be improved by increasing the tool hardness, high ductility and decreasing of friction coefficient between the tool and the work material. In a similar way, resistance to galling can be increased by increasing the tool hardness and decreasing of friction. The purpose of this project was to investigate the use of Vancron 40 as work rolls in cold rolling of stainless steel in cluster rolling mills. Considerable factors were among others, the influence of different industrial lubricants, minimizing of temperature rising during rolling, lowering of rolling forces, longer life of rolls, easier grinding of rolls, increase the oil film bearing at normal cold rolling conditions and improving surface roughness of the final products.

    For using of work rolls in cold rolling cluster mills, roll material Vancron 40 was evaluated with regard to roll wear, surface quality and galling. Currently used roll type ASP23 was used as reference roll in the evaluation. The experiments were performed, as much as possible, in accordance to steel industries recommendations. The experiments were conducted with a 4-high pilot rolling mill at Swerea MEFOS in Luleå which is equipped for rolling of both flat and long products. The experiment was done for different industrial mineral-based lubricants. Lubrication was applied in a controlled form to the upper and lower work rolls and in the contact zone. To achieve the proposed final thickness, five passes were rolled. The characteristic of the upper and the lower work rolls, during rolling, was also examined. The pilot experimental results gave promising result in surface roughness, galling and roll material hardness. Due to its chemical and physical properties, Vancron 40 is believed to be the best solution to resist adhesive wear and galling in cold rolling process that require higher accuracy. 

  • 310. Thirathipviwat, P.
    et al.
    Song, G.
    Jayamani, Jayaraj
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Bednarcik, J.
    Wendrock, H.
    Gemming, T.
    Freudenberger, J.
    Nielsch, K.
    Han, J.
    A comparison study of dislocation density, recrystallization and grain growth among nickel, FeNiCo ternary alloy and FeNiCoCrMn high entropy alloy2019Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 790, s. 266-273Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The microstructural evolutions in terms of dislocation density, annealing twin density as well as with respect to microstructural changes due to recrystallization and grain growth were investigated in pure Ni, equiatomic FeNiCo alloy, and FeNiCoCrMn high entropy alloy (HEA) during the thermomechanical process. All samples were single phase and showed a face-centered cubic (FCC) lattice structure. This was maintained during thermomechanical processing comprising of cold swaging by 85% reduction of cross-sectional area and subsequent annealing at 800 °C. The level of dislocation accumulation during cold swaging increased with the number of constituent elements. The FeNiCoCrMn HEA obtained the highest dislocation density, followed by the FeNiCo and Ni, respectively. After the annealing at 800 °C for 0.5 h, all samples achieved the large fraction of recrystallized grains with minor fraction of substructured grains and no deformed grain. The FeNiCoCrMn HEA obtained the smallest recrystallized grain size (∼5 μm) after the annealing at 800 °C for 0.5 h. This could be a result of the highest dislocation density generated during cold swaging prior to the annealing. The prolonged annealing at 800 °C for up to 24 h led to a grain growth for all the samples, however, at different growth rates. The FeNiCoCrMn HEA revealed the lowest rate of grain growth, but the microstructural changes during the annealing were not significantly different between the FeNiCo and Ni samples. Besides the effect of the number of constituent elements, the type and the combination of constituent elements have an effect on the microstructural evolution during the annealing.

  • 311.
    Tunell, Helena
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Osterman, Jesper
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Selo, Muhammed
    POLY 701-Photoinduced reorientation and LC alignment of novel azobenzene containing polymers2006Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 232Artikel i tidskrift (Övrigt vetenskapligt)
  • 312.
    Tunell, Helena
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Selo, Muhammed
    Skarp, Kent
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Hilborn, Johns
    Synthesis and characterization of main chain polyimides containing chalcone derivatives for LC alignment2006Ingår i: Polymer journal, ISSN 0032-3896, E-ISSN 1349-0540, Vol. 38, nr 7, s. 716-723Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two soluble polyimides containing chalcone derivatives in the main chains were successfully prepared using the Mitsunobu reaction at room temperature, reacting diols with diimides. With this reaction procedure the high temperature imidization step normally needed for the synthesis of polyimides is avoided and the polymers can be used for temperature sensitive applications. The main chain polyimides were characterized with FT-IR, NMR and DSC and the extent of the photoreaction was measured with FT-IR and UV-vis spectroscopy. Isobestic points were observed in the absorption spectral changes at the early stage of UV irradiation as a result of a single photochemical process. Further photoirradiation is accompanied by deviation from the isobestic points, implying that another photochemical process has started. With FT-IR investigations it was concluded that photodimerization is the process occurring at low UV exposure doses and that trans-cis isomerization is starting simultaneously at higher doses. The optical anisotropic properties were investigated upon exposure of the polymers as thin films to linearly polarized UV (LPUV) light of different doses. Selected crosslinking in the parallel direction relative to the direction of the LPUV light and subsequent optical anisotropy in the film were achieved.

  • 313.
    Vainikainen, Kalevi
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Undersökning av sprickors uppträdande och beteende vid valsning av rostfri tråd;: Investigation of Surface Cracks Behaviour in Wire Rod Rolling of Stainless Steel2006Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    Marknaden ställer allt högre krav på rostfri valstråd samtidigt som många stålsorter är komplicerade att tillverka. Defekter av olika slag får inte förekomma på kallstukningstråd, fjädertråd och på tråd för andra krävande applikationer. Sprickor som är svåra att upptäcka kan hamna hos kunden, vilket leder till reklamationer. Därmed undersöktes sprickors beteende under valsning genom hela valsverket. Ämnen i olika stålsorter preparerades med längsgående sprickor, värmdes i förvärmningsugnen och valsades till tråd i dimensionen Ø 5,6 mm. Prover togs ut vid befintliga saxar och på färdig tråd. En undersökning gjordes även på en repa som introducerades i början av den kontinuerliga mellansträckan, prover togs ut på samma sätt som för sprickor. Efter provberedning mättes sprickorna med hjälp av ljusmikroskop och analyserades i SEM. Sedan redovisades sprickdjupet genom hela valsverket som ett relativt sprickdjup. Resultaten visade att i de första sticken påverkade formen på sprickan och repan sprickdjupet markant, placeringen i spåret hade också en betydelse. Det kunde konstateras att en ökad sprickbredd med innesluten oxid påverkade sprickdjupet negativt. Sprickdjupet påverkades även av stålets analys. Slutligen kunde konstateras att två av stålsorterna var känsligare för sprickor och att de preparerade sprickorna och den introducerade repan inte kunde elimineras för någon av stålsorterna.

  • 314.
    Valyukh, Iryna
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Arwin, Hans
    Chigrinov, Vladimir
    Valyukh, Sergiy
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Characterization of the photo-alignment material SD-1/SDA-2 with spectroscopic ellipsometry2007Ingår i: IDW '07: Proceedings of the 14th International Display Workshops, vols 1-3, 2007, Vol. 1-3, s. 391-394Konferensbidrag (Refereegranskat)
    Abstract [en]

    Variable angle spectroscopic ellipsometry (VASE) is applied for investigation of the azo-dye SD-1/SDA-2 which are used for photoalignment of liquid crystals. The azo-dye was spin coated on silicon substrates. Samples as prepared as well as samples illuminated with polarized UV light were studied. The measured optical constants were modelled with an ensemble of the Lorentz oscillators. The results confirm the reorientation mechanism of the photo-induced order formation in the azo-dye films under the action of polarized light, and also show that there exist some photochemical processes.

  • 315.
    Valyukh, Iryna
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Arwin, Hans
    Chigrinov, Vladimir
    Valyukh, Sergiy
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    UV-induced in-plane anisotropy in layers of mixture of the azo-dyes SD-1/SDA-2 characterized by spectroscopic ellipsometry2008Ingår i: Physica Status Solidi C - Current topics in solid state physics, vol.5, no.5, 2008, Vol. 5, nr 5, s. 1274-1277Konferensbidrag (Refereegranskat)
    Abstract [en]

    The optical properties of the azo-dyes SD-1/SDA-2, which are used for photoaligning of liquid crystals (LCs), are investigated with Variable Angle Spectroscopic Ellipsometry (VASE). Films of mixture of SD-1/SDA-2 are deposited by spin coating on silicon wafers. The estimated thickness is approximately 10 nm. To achieve photo-induced anisotropy, one of the samples is illuminated during 15 minutes with linearly polarized UV light followed by thermal stabilization during 1 hour at 150 degrees C. VASE measurements are performed in the wavelength range 200-1350 rim at several angles of incidence and at different sample orientations. Dielectric functions of azo-dye films without/with polarized UV light illumination were modelled using an ensemble of Lorentz oscillators. The results confirm the diffusion model proposed recently for explanation of the formation of the photo-induced order in azo-dye films under the action of polarized light. Refractive indices, their wavelength dispersion and thicknesses of films of SD-1/SDA-2 are reported here.

  • 316.
    Valyukh, Iryna
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Green, S.
    Arwin, H.
    Niklasson, G. A.
    Wäckelgård, Ewa
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Granqvist, C. G.
    Spectroscopic ellipsometry characterization of electrochromic tungsten oxide and nickel oxide thin films made by sputter deposition2010Ingår i: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 94, nr 5, s. 724-732Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electrochromic films of tungsten oxide and nickel oxide were made by reactive dc magnetron sputtering and were characterized by X-ray diffraction, Rutherford backscattering spectrometry, scanning electron microscopy, and atomic force microscopy. The optical properties were investigated in detail by spectroscopic ellipsometry and spectrophotometry, using a multiple-sample approach. The W-oxide film was modeled as a homogeneous isotropic layer, whereas the Ni-oxide film was modeled as an anisotropic layer with the optical axis perpendicular to the surface. Parametric models of the two layers were then used to derive complex refractive index in the 300-1700 nm range, film thickness, and surface roughness. A band gap of 3.15 eV was found for the W-oxide film, using a Tauc-Lorentz parameterization. For the Ni-oxide film, taken to have direct optical transitions, band gaps along the optical axis, perpendicular to it, and in an isotropic intermediate layer at the bottom of the film were found to be 3.95, 3.97, and 3.63 eV, respectively. Parameterization for the Ni oxide was made by use of the Lorentz model. (C) 2009 Elsevier B.V. All rights reserved.

  • 317.
    Valyukh, Iryna
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Slobodyanyuk, A
    Valyukh, S
    Osterman, Jesper
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Skarp, Kent
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Using the Jones matrix for simulation of light propagation in anisotropic media2003Ingår i: Journal of optical technology (Print), ISSN 1070-9762, E-ISSN 1091-0786, Vol. 70, nr 7, s. 470-473Artikel i tidskrift (Refereegranskat)
  • 318.
    Valyukh, Iryna
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Slobodyanyuk, A.
    Valyukh, S.
    Sorokin, V.
    Osterman, Jesper
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Skarp, Kent
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    On accuracy of the Jones matrix method for simulation of light propagation in twisted nematic liquid crystals2002Ingår i: Proc. of the 11th Int. Symp. Advanced Display Technologies, UkraineArtikel i tidskrift (Refereegranskat)
  • 319.
    Valyukh, Iryna
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Slobodyanyuk, A.
    Valyukh, S.
    Sorokin, V.
    Osterman, Jesper
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Skarp, Kent
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Simulation of light scattered by reflective polarizer with a rough metallic surface2002Ingår i: Eurodisplay 2002, Nice, France, 2002Konferensbidrag (Refereegranskat)
  • 320.
    Valyukh, Iryna
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Valyukh, S.
    Skarp, Kent
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Theoretical study of the optical properties of low voltage stacked cholesteric liquid-crystal displays2004Ingår i: Asia display, 2004Konferensbidrag (Refereegranskat)
  • 321.
    Valyukh, Iryna
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Valyukh, Sergiy
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Arwin, H.
    Chigrinov, V.
    Characteristic functions for uniformly twisted birefringent media2007Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 102, nr 6, artikel-id 063110Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present two functions for characterization of birefringent media with application to twisted nematic liquid crystal (LC) cells in the field off state. The first function is for reflective LC cells and the second is for transmissive LC cells. Based on the Stockes formalism, it is shown that these functions describe the ability of a layer of the twisted birefringent medium to change polarization of the output light and are invariant to the layer orientation. The characteristic functions are found in simple procedures and can be used for simultaneous determination of retardation, its wavelength dispersion, and twist angle, as well as for solving optimization problems. © 2007 American Institute of Physics.

  • 322.
    Valyukh, Iryna
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Valyukh, Sergiy
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Skarp, Kent
    Chigrinov, V.
    Monochromatic bistable reflective and transfiective ferroelectric LCDs2005Ingår i: Proceedings of the 25th International Display Research Conference, Eurodisplay 2005, 2005, s. 305-308Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study single and double polarizer monochromatic bistable reflective and transfective direct view ferroelectric liquid crystal displays (FLCDs). Three types of monochromatic displays are considered Black & White, Black & Yellow, Black & Green. Theoretical approach for finding optimal parameters of an FLCD is presented.

  • 323.
    Valyukh, Sergiy
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Adas, C.
    Franklin, G.
    Skarp, K.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Measuring parameters of liquid crystal cells with MePaLC system2005Ingår i: IDMC 2005: Proceedings of the International Display Manufacturing Conference, 2005, s. 795-798Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a sytem MePaLC for measuring retardation, its wavelength dispersion, twist angle, cell gap, and orientation of the input director. MePaLC enables us to measure practically all types of nematic liquid crystal cells: reflective and transmissive ones, with small and large cell gap.

  • 324.
    Valyukh, Sergiy
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Osterman, Jesper
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Adås, C.
    Skarp, Kent
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Cell gap measurements of flexible reflective TN- and STN-LC cells2004Ingår i: SID international symposium, 2004Konferensbidrag (Refereegranskat)
  • 325.
    Valyukh, Sergiy
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Osterman, Jesper
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Skarp, Kent
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Simple Spectroscopic Method to Measure Cell Gap and Twist Angle of TN-LCD2003Ingår i: International display research conference, 2003Konferensbidrag (Refereegranskat)
  • 326.
    Valyukh, Sergiy
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Osterman, Jesper
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Skarp, Kent
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Chigrinov, V.
    Optical performance of bistable reflective and transflective ferroelectric LCDs2005Ingår i: SID international symposium, Boston, 2005Konferensbidrag (Refereegranskat)
  • 327.
    Valyukh, Sergiy
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Osterman, Jesper
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Valyuhk, Iryna
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Skarp, Kent
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Characterization of flexible reflective liquid crystal cells2005Ingår i: Journal of the Society for Information Display, ISSN 1071-0922, E-ISSN 1938-3657, Vol. 13, nr 6, s. 501-506Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider peculiarities in testing flexible reflective liquid-crystal (LC) cells. Several new methods for measuring optical retardation of filled reflective LC cells on plastic substrates are proposed. Cases when the plastic is anisotropic and the LC cell consists of either one or two internal polarizers are studied. The majority of proposed methods can be applied for transmissive LC cells as well as for measuring twist angle.

  • 328.
    Valyukh, Sergiy
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Rybalochka, A.
    Sorokin, V.
    Slobodyanyuk, A.
    Spectroscopic method to measure cellgap of TN LC cells2002Ingår i: Proc. of Eurodisplay 2002, NiceArtikel i tidskrift (Övrigt vetenskapligt)
  • 329.
    Valyukh, Sergiy
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Rybalochka, A.
    Sorokin, V.
    Tytarenko, P.
    Skarp, Kent
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    A method for measuring reflective twist nematic liquid crystal cell properties2003Ingår i: Advanced display technologies, Moscow, Russia, 2003Konferensbidrag (Refereegranskat)
  • 330.
    Valyukh, Sergiy
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Rybalochka, A
    Sorokin, V
    Tytarnenko, T
    Skarp, Kent
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    A method for measuring reflective twist nematic liquid crystal cell proporties2003Ingår i: Proceedings of XII International Symposium Advanced Display Technologies, Moscow, Russia, 2003, s. 254-257Konferensbidrag (Refereegranskat)
  • 331.
    Valyukh, Sergiy
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Slobodyanyuk, A.
    Sorokin, V.
    Skarp, Kent
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Computer simulation of scattering properties of cholesteric liquid crystal displays2001Ingår i: European conference on liquid crystals, Halle, Germany, 2001Konferensbidrag (Övrigt vetenskapligt)
  • 332.
    Valyukh, Sergiy
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Valyuhk, Iryna
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Skarp, Kent
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Spectrophotometric determination of reflective liquid crystal cell parameters2006Ingår i: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 99, nr 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We introduce a method for the determination of the optical retardation, its wavelength dispersion, the cell twist angle, and the orientation of the input director in a reflective liquid crystal (LC) cell. These parameters are found from the extremes of a characteristic function defined as a sum of two spectral reflectivities of the LC cell placed between a pair of linear polarizers. The reflectivities are measured for two cell orientations, one of which is arbitrary and the other one is turned through 45°. Both theoretical analysis and experimental procedures are presented. Excellent agreement between the experiment and our theory has been found. The proposed method can be applied to the measurement of reflective LC cells with small and large cell gaps, as well as cells with small and large twist angles.

  • 333.
    Valyukh, Sergiy
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Valyukh, Iryna
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Adås, C.
    Chigrinov, V.
    Skarp, Kent
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Reflective liquid crystal cell parameters2004Ingår i: Asia display, 2004Konferensbidrag (Refereegranskat)
  • 334.
    Valyukh, Sergiy
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Valyukh, Iryna
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Xu, Peizhi
    Chigrinov, Vladimir
    Study on birefringent color generation for a reflective ferroelectric liquid crystal display2006Ingår i: Japanese Journal of Applied Physics, ISSN 0021-4922, E-ISSN 1347-4065, Vol. 45, nr 10A, s. 7819-7826Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the possibility of a layer of a surface stabilized ferroelectric liquid crystal coupled with several retardation plates for birefringent color generation. Double and single polarizer reflective bistable dichromatic ferroelectric liquid crystal displays are considered. We demonstrate that one or two retardation plates are sufficient for a display having good color characteristics and high brightness. Optimal parameters for green/red and blue/yellow ferroelectric liquid crystal displays are found.

  • 335. Vattur Sundaram, M.
    et al.
    Surreddi, Kumar Babu
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Hryha, E.
    Veiga, A.
    Berg, S.
    Castro, F.
    Nyborg, L.
    Enhanced densification of PM steels by liquid phase sintering with boron-containing master alloy2017Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 49A, nr 1, s. 255-263Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reaching high density in PM steels is important for high-performance applications. In this study, liquid phase sintering of PM steels by adding gas-atomized Ni-Mn-B master alloy was investigated for enhancing the density levels of Fe- and Mo- prealloyed steel powder compacts. The results indicated that liquid formation occurs in two stages, beginning with the master alloy melting (LP-1) below and eutectic phase formation (LP-2) above 1373 K (1100 °C). Mo and C addition revealed a significant influence on the LP-2 temperatures and hence on the final densification behavior and mechanical properties. Microstructural embrittlement occurs with the formation of continuous boride networks along the grain boundaries, and its severity increases with carbon addition, especially for 2.5 wt pct of master alloy content. Sintering behavior, along with liquid generation, microstructural characteristics, and mechanical testing revealed that the reduced master alloy content from 2.5 to 1.5 wt pct (reaching overall boron content from 0.2 to 0.12 wt pct) was necessary for obtaining good ductility with better mechanical properties. Sintering with Ni-Mn-B master alloy enables the sintering activation by liquid phase formation in two stages to attain high density in PM steels suitable for high-performance applications. © 2017 The Author(s)

  • 336.
    Vattur Sundaram, Maheswaran
    et al.
    Department of Materials and Manufacturing Technology, Chalmers University of Technology, Gothenburg, Sweden .
    Karlsson, Henrik
    Volvo Group Trucks Technology, Gothenburg, Sweden.
    Surreddi, Kumar Babu
    Chalmers University of Technology, Gothenburg.
    Hryha, Eduard
    Department of Materials and Manufacturing Technology, Chalmers University of Technology, Gothenburg, Sweden .
    Andersson, Michael
    Höganäs AB, Höganäs, Sweden.
    Åkerström, Gunnar
    Volvo Group Trucks Technology, Gothenburg, Sweden.
    Nyborg, Lars
    Department of Materials and Manufacturing Technology, Chalmers University of Technology, Gothenburg, Sweden .
    Investigation of Low Temperature Creep Behaviour of PM Steels2014Ingår i: Powder Metallurgy Progress, ISSN 1335-8987, Vol. 14, nr 2, s. 67-72Artikel i tidskrift (Refereegranskat)
  • 337.
    Vattur Sundaram, Maheswaran
    et al.
    Chalmers University of Technology.
    Surreddi, Kumar Babu
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Hryha, Eduard
    Chalmers University of Technology.
    Veiga, Angela
    CEIT, Pº Manuel Lardizábal 15, 20018 San Sebastián, Spain.
    Berg, Siguard
    Höganäs AB, SE-263 83 Höganäs, Sweden.
    Castro, Francisco
    CEIT, Pº Manuel Lardizábal 15, 20018 San Sebastián, Spain.
    Nyborg, Lars
    Chalmers University of Technology.
    Full Densification in PM Steels Through Liquid Phase Sintering and HIP Approach2018Ingår i: Euro PM2018 Proceedings, 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    High-density powder metallurgy (PM) components are required for high-performance applications. Liquid phase sintering (LPS) is one such method to improve the densification, especially the master alloy route is preferred due to the flexibility in tailoring the alloying contents. In this study, gas atomised Ni-Mn-B master alloy powder of size fraction < 45 µm was admixed with water atomised iron and Mo-prealloyed powder. During sintering, there was a significant densification due to LPS where the liquid formation occurred in two stages, one from the master alloy melting and another from the eutectic liquid formation, enabling densities > 95%. The microstructural investigation revealed that the surface densification was achieved after sintering in H2 containing atmosphere. Capsule free hot isostatic pressing was performed on these samples to achieve full density. This approach of combining LPS and capsule free hot isostatic pressing demonstrates the potential in reaching full densification in high-performance PM steel components.

  • 338. Vetrivendan, E.
    et al.
    Jayamani, Jayaraj
    Ningshen, S.
    Mallika, C.
    Kamachi Mudali, U.
    Argon Shrouded Plasma Spraying of Tantalum over Titanium for Corrosion Protection in Fluorinated Nitric Acid Media2018Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, nr 3, s. 512-523Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Argon shrouded plasma spraying (ASPS) was used to deposit a Ta coating on commercially pure Ti (CP-Ti) under inert argon, for dissolver vessel application in the aqueous spent fuels reprocessing plant with high plutonium content. Oxidation during plasma spraying was minimized by shrouding argon system. Porosity and oxide content were controlled by optimizing the spraying parameters, to obtain a uniform and dense Ta coating. The Ta particle temperature and velocity were optimized by judiciously controlling the spray parameters, using a spray diagnostic charge-coupled device camera. The corrosion resistance of the Ta coatings developed by ASPS was investigated by electrochemical studies in 11.5 M HNO3 and 11.5 M HNO3 + 0.05 M NaF. Similarly, the durability of the ASPS Ta coating/substrate was evaluated as per ASTM A262 Practice-C test in boiling nitric acid and fluorinated nitric acid for 240 h. The ASPS Ta coating exhibited higher corrosion resistance than the CP-Ti substrate, as evident from electrochemical studies, and low corrosion rate with excellent coating stability in boiling nitric, and fluorinated nitric acid. The results of the present study revealed that tantalum coating by ASPS is a promising strategy for improving the corrosion resistance in the highly corrosive reprocessing environment.

  • 339. Vida, Á.
    et al.
    Maksa, Z.
    Molnar, David
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik. KTH.
    Huang, S.
    Kovac, J.
    Varga, L. K.
    Vitos, L.
    Chinh, N. Q.
    Evolution of the phase structure after different heat treatments in NiCoFeCrGa high entropy alloy2018Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 743, s. 234-239Artikel i tidskrift (Refereegranskat)
  • 340. Wang, Z.
    et al.
    Prashanth, K. G.
    Surreddi, Kumar Babu
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Suryanarayana, C.
    Eckert, J.
    Scudino, S.
    Pressure-assisted sintering of Al–Gd–Ni–Co amorphous alloy powders2018Ingår i: Materialia, ISSN 2589-1529, Vol. 2, s. 157-166Artikel i tidskrift (Refereegranskat)
  • 341.
    Westin, Tommy
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Induktiv provning av ferritiskt rostfritt stå2011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The report examines the factors which may be a contributing cause to the problems that are present when ferritic stainless steel are eddy current tested in a warm condition. The work is carried out at Fagersta Stainless AB in Fagersta which manufactures stainless steel wire. In the rolling mill there is an eddy current equipment for detection of surface defects on the wire. The ferritic stainless steels cause a noise when testing and this noise complicates the detection of defects.Because of this, a study was made of how the noise related to factors such as steel grade, temperature, size and velocity. By observing the signal and with the possibilities to change the equipment settings the capability to let a signal filter reduce the noise level were evaluated. Theories about the material's physical properties have also been included, mainly the magnetic properties, electrical conductivity and the material's tendency to oxidize.Results from the tests show that a number of factors do not affect the inductive test significantly and to use a filter to reduce the noise level does not seem to be a viable option. The level of noise does not relate to the presence of superficial particles in form of oxides.The ferritic stainless steels showed some difference in noise level. Which noise level there was did match well with the steels probability for a precipitation of a second phase, and precipitation of austenite may in this case contribute to noise when using an eddy current instrument.The noise is probably due to some physical material property that varies within the thread.

  • 342.
    Westlund, V.
    et al.
    Uppsala Univ, Angstrom Tribomat Grp, Box 534, S-75121 Uppsala, Sweden..
    Heinrichs, J.
    Uppsala Univ, Angstrom Tribomat Grp, Box 534, S-75121 Uppsala, Sweden..
    Olsson, Mikael
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik. Uppsala Univ, Angstrom Tribomat Grp, Box 534, S-75121 Uppsala, Sweden.
    Jacobson, S.
    Uppsala Univ, Angstrom Tribomat Grp, Box 534, S-75121 Uppsala, Sweden..
    Investigation of material transfer in sliding friction-topography or surface chemistry?2016Ingår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 100, s. 213-223Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To differentiate between the roles of surface topography and chemical composition on influencing friction and transfer in sliding contact, a series of tests were performed in situ in an SEM. The initial sliding during metal forming was investigated, using an aluminum tip representing the work material, put into sliding contact with a polished flat tool material. Both DLC-coated and uncoated tool steel was used. By varying the final polishing step of the tool material, different surface topographies were obtained. The study demonstrates the strong influence from nano topography of an unpolished DLC coated surface on both coefficient of friction and material transfer. The influence of tool surface chemistry is also discussed.

  • 343.
    Wiklund, Urban
    et al.
    Uppsala University.
    Olsson, Mikael
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Jacobson, Staffan
    Uppsala University.
    Degradation mechanisms of matrix steel in rock drill bits2016Ingår i: Proceedings of the 17th Nordic Symposium on Tribology - Nordtrib 2016, 2016Konferensbidrag (Refereegranskat)
  • 344. Wikström, Lars
    et al.
    Bexell, Ulf
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Lindgren, Michael
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Partial annealing of stainless steel before roll forming2007Ingår i: Stål 2007, 2007Konferensbidrag (Övrigt vetenskapligt)
  • 345.
    Yvell, Karin
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik. KTH, Materialvetenskap.
    Experimental Studies of Deformation Structures in Stainless Steels using EBSD2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this thesis, the focus has been the study of deformation structures in stainless steels by using electron backscatter diffraction (EBSD). Via increased knowledge of the evolution of the substructure during deformation, the design and control of the manufacturing process can be improved.

    A relation was found between the active deformation mechanisms, the evolution of low angle boundaries (LABs) and the strain hardening rate. When deformation twinning was an active deformation mechanism in an austenitic stainless steel with lower stacking fault energy (SFE), the strain hardening rate was maintained up to large strains due to formation of LABs. The deformation twin boundaries acted as new obstacles for dislocation slip which in turn increased the formation of LABs even further. During deformation by slip in an austenitic stainless steel with a higher SFE, the strain hardening rate instead decreased when LABs were formed. A high value of SFE promotes dislocation cross slip which in turn increases annihilation of dislocations leading to a minor increase in LAB formation.

    Deformation structures formed in surface grains during in situ tensile tests were found to develop at lower strains than in bulk grains obtained from interrupted conventional tensile tests. This behavior is consistent with the fact that dislocations sources and deformation twinning operate at approximately half the stress on a free surface as compared to the bulk.

    The deformation structures were quantified by measuring size distributions for entities bounded by LABs and high angle boundaries (HABs). The size distributions were found to be well described by bimodal lognormal distribution functions. The average size for the distribution of small grains and subgrains correlated well with the mean free distance of dislocation slip and to the strain hardening.

  • 346.
    Yvell, Karin
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik. KTH, Materialvetenskap.
    Engberg, Göran
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Deformation structures in a duplex stainless steel2018Ingår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 941, s. 176-181Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The evolution of the deformation structure with strain has been studied using electron backscatter diffraction (EBSD). Samples from interrupted uniaxial tensile tests and from a cyclic tension/compression test were investigated. The evolution of low angle boundaries (LABs) was studied using boundary maps and by measuring the LAB density. From calculations of local misorientations, smaller orientation changes in the substructure can be illustrated. The different orientations developed with strain within a grain, due to operation of different slip systems in different parts of the grain, were studied using a misorientation profile showing substantial orientation changes after a true strain of 0.24. The texture evolution with increasing strain was followed by using inverse pole figures (IPFs). The observed substructure development in the ferritic and austenitic phases could be successfully correlated with the stress-strain curve from a tensile test. LABs were first observed in the different phases when the strain hardening rate changed in appearance indicating that cross slip started to operate as a significant dislocation recovery mechanism. The evolution of the deformation structure is concluded to occur in a similar manner in the austenitic and ferritic phases but with different texture evolution for the two phases.

  • 347.
    Yvell, Karin
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Engberg, Göran
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Microstructure evolution in an austenitic stainless steel during wire rolling2013Ingår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 753, s. 407-410Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Material characterization is of great importance for example to improve and further develop physically based models for predicting the microstructural evolution in steels during and after hot deformation. The aim of this study was to characterize the microstructure evolution during wire rod rolling of an austenitic stainless steel of type AISI 304L in a wire rod block, consisting of eight pairs of rolls, using electron backscatter diffraction. The investigation showed that the grain size in the center of the bar decreases during the first four passes. The grain size decrease from 6.5 Όm after the first roll pass down to 2 Όm, and only small changes was measured in the overall grain size during the last four passes. The subgrain size adopts an almost constant size of 0.9 Όm from the second until the fifth roll pass. During the first 3 passes almost no recrystallization is observed and strain accumulates. Partial recrystallization then starts and for the last 3 passes the recrystallization is almost complete and the texture is nearly random. © (2013) Trans Tech Publications, Switzerland.

  • 348.
    Yvell, Karin
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Grehk, T. M.
    Engberg, Göran
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Microstructure characterization of 316L deformed at high strain rates using EBSD2016Ingår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 122, s. 14-21Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Specimens from split Hopkinson pressure bar experiments, at strain rates between ~ 1000–9000 s− 1 at room temperature and 500 °C, have been studied using electron backscatter diffraction. No significant differences in the microstructures were observed at different strain rates, but were observed for different strains and temperatures. Size distribution for subgrains with boundary misorientations > 2° can be described as a bimodal lognormal area distribution. The distributions were found to change due to deformation. Part of the distribution describing the large subgrains decreased while the distribution for the small subgrains increased. This is in accordance with deformation being heterogeneous and successively spreading into the undeformed part of individual grains. The variation of the average size for the small subgrain distribution varies with strain but not with strain rate in the tested interval. The mean free distance for dislocation slip, interpreted here as the average size of the distribution of small subgrains, displays a variation with plastic strain which is in accordance with the different stages in the stress-strain curves. The rate of deformation hardening in the linear hardening range is accurately calculated using the variation of the small subgrain size with strain.

  • 349.
    Yvell, Karin
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Grehk, T. M.
    Hedström, P.
    Borgenstam, A.
    Engberg, Göran
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    EBSD analysis of surface and bulk microstructure evolution during interrupted tensile testing of a Fe-19Cr-12Ni alloy2018Ingår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 141, s. 8-18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract The microstructure evolution in both surface and bulk grains in a pure Fe-19Cr-12Ni alloy has been analyzed using electron backscatter diffraction after tensile testing interrupted at different strains. Surface grains were studied during in situ tensile testing performed in a scanning electron microscope, whereas bulk grains were studied after conventional tensile testing. The evolution of the deformation structure in surface and bulk grains displays a strong resemblance but the strain needed to obtain a similar deformation structure is lower in the case of surface grains. Both slip and twinning are observed to be important deformation mechanisms, whereas deformation-induced martensite formation is of minor importance. Since the stacking fault energy (SFE) is low, 17mJ/m2, dynamic recovery by cross slip of un-dissociated dislocations is unfavorable. This reduces the annihilation of dislocations which in turn leads to a significant increase of low angle boundaries with increasing strain. The low SFE also favors formation of deformation twins which reduces the slip distance, leading to a hardening similar to the Hall-Petch relation. The combination of a low ability for cross-slip and a reduced slip distance caused by twinning is concluded to be the main reason for maintaining a high strain-hardening rate up to strains close to necking.

  • 350.
    Yvell, Karin
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Grehk, T. M.
    Hedström, P.
    Borgenstam, A.
    Engberg, Göran
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Microstructure development in a high-nickel austenitic stainless steel using EBSD during in situ tensile deformation2018Ingår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 135, nr Supplement C, s. 228-237Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Plastic deformation of surface grains has been observed by electron backscatter diffraction technique during in situ tensile testing of a high-nickel austenitic stainless steel. The evolution of low- and high-angle boundaries as well as the orientation changes within individual grains has been studied. The number of low-angle boundaries and their respective misorientation increases with increasing strain and some of them also evolve into high-angle boundaries leading to grain fragmentation. The annealing twin boundaries successively lose their integrity with increasing strain. The changes in individual grains are characterized by an increasing spread of orientations and by grains moving towards more stable orientations with 〈111〉 or 〈001〉 parallel to the tensile direction. No deformation twins were observed and deformation was assumed to be caused by dislocation slip only.

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