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  • 1.
    Al-Saadi, Munir
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. R&D Metallurgy, AB Sandvik Materials Technology, SE-811 81 Sandviken, Sweden.
    Hulme-Smith, Christopher
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Sandberg, Fredrik
    R&D Metallurgy, AB Sandvik Materials Technology, SE-811 81 Sandviken, Sweden.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Hot Deformation Behaviour and Processing Map of Cast Alloy 825Manuscript (preprint) (Other academic)
    Abstract [en]

    Alloy 825 is a nickel-based alloy that is commonly used in applications where both high strength and corrosion resistance are required. Applications include tanks in the chemical, food and petrochemical industries and oil and gas pipelines. Components made from Alloy 825 are often manufactured using hot deformation. However, there is no systematic study to optimise the processing conditions reported in literature. In this study, a processing map for as-cast Alloy 825 is established to maximise the power dissipation efficiency of hot deformation and correlate the processing conditions to final materials properties. The hot deformation behaviour of equiaxed Alloy 825 is characterized on the basis of the dynamic materials model and compression data in the temperature range of 950 °C to 1250 °C at an interval of 50°C and strain rate range of 0.01 s-1 to 10 s-1 to a true strain of 0.7 using a Gleeble-3500 thermomechanical simulator. Flow stress is modelled by the constitutive equation based on a hyperbolic sine function. The deformed material is characterized using Vickers hardness, optical microscopy and scanning electron microscopy, including electron backscattered diffraction. The true stress-true strain curves exhibit peak stresses followed by softening due to occurrence of dynamic recrystallization. The value of stress exponent in the hyperbolic sine-based constitutive equation, n=5.0. This suggests that the rate-limiting mechanism of deformation is climb (diffusion)-mediated dislocation glide. The activation energy for plastic flow in the temperature range tested is about 450 kJ mole-1, and the relationship between flow stress and temperature-compensated strain rate (via the Zener-Hollomon parameter) was found to be valid across this temperature range. The maximum power dissipation efficiency is over 35%. The highest efficiency is observed over temperature range of 1100 °C – 1250 °C and a strain rate of 0.01 s-1 – 0.1s-1. These are the optimum conditions for hot working. The optimum processing parameters for good strain hardening are obtained in the temperature range of between  950 °C  and  1100 °C with a strain rate between  0.3/s  and 10.0/s. 

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  • 2.
    Al-Saadi, Munir
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. R&D, AB Sandvik Materials Technology, SE-811 81 Sandviken.
    Sandberg, Fredrik
    R&D, AB Sandvik Materials Technology, SE-811 81 Sandviken.
    Hulme-Smith, Christopher
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Modelling of strengthening mechanisms in wrought nickel-based 825 alloy subjected to solution annealing2021In: Metals, ISSN 2075-4701, Vol. 11, no 5, p. 771-20Article in journal (Refereed)
    Abstract [en]

    Wrought nickel‐based Alloy 825 is widely used in the oil and gas industries, attributed toits high strength at temperatures up to 540 °C. However, differences in mechanical properties arisein finished components due to variations in both grain size and dislocation density. Numerous ex‐perimental studies of the strengthening mechanisms have been reported and many models havebeen developed to predict strengthening under thermomechanical processing. However, there aredebates surrounding some fundamental issues in modeling and the interpretation of experimentalobservations. Therefore, it is important to understand the evolution of strain within the materialduring the hot‐forging process. In addition, there is a lack of research around the behavior duringhot deformation and subsequent stabilization of Alloy 825. This article investigates the origin of thisstrength and considers a variety of strengthening mechanisms, resulting in a quantitative predictionof the contribution of each mechanism. The alloy is processed with a total forging strain of 0.45, 0.65,or 0.9, and subsequent annealing at a temperature of 950 °C, reflecting commercial practice. Themicrostructure after annealing is similar to that before annealing, suggesting that static recovery isdominant at this temperature. The maximum yield strength and ultimate tensile strength were348 MPa and 618 MPa, respectively, obtained after forging to a true strain of 0.9, with a ductility of40%. The majority of strengthening was attributed to grain refinement, the dislocation densities thatarise due to the large forging strain deformation, and solid solution strengthening. Precipitatestrengthening was also quantified using the Brown and Ham modification of the Orowan bowingmodel. The results of yield strength calculations are in excellent agreement with experimental data,with less than 1% difference. The interfacial energy of Ti(C,N) in the face‐centered cubic matrix of. These results can bethe current alloy has been assessed for the first time, with a value of 0.8 mJm−2used by future researchers and industry to predict the strength of Alloy 825 and similar alloys, es‐pecially after hot‐forging.

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  • 3.
    Al-Saadi, Munir
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing. R&D, AB Sandvik Materials Technology, SE-811 81Sandviken, Sweden..
    Sandberg, Fredrik
    R&D, AB Sandvik Materials Technology, SE-811 81Sandviken, Sweden..
    Hulme-Smith, Christopher
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    A study of the static recrystallization behaviour of cast Alloy 825 after hot-compressions2019In: Journal of Physics: Conference Series, 2019, Vol. 1270, article id 012023Conference paper (Refereed)
    Abstract [en]

    The static recrystallization behaviour of a columnar and equiaxed Alloy 825 material was studied on a Gleeble-3800 thermo-simulator by single-hit compression experiments. Deformation temperatures of 1000-1200 °C, a strain of up to 0.8, a strain rate of 1s-1, and relaxation times of 30, 180, and 300 s were selected as the deformation conditions to investigate the effects of the deformation parameters on the SRX behaviour. Furthermore, the influences of the initial grain structures on the SRX behaviors were studied. The microstructural evolution was studied using optical microscopy and EBSD. The EBSD measurements showed a relaxation time of 95 % for fractional recrystallization grains, 𝑡95, in both structures, was less than 30 seconds at the deformation temperatures 1100 °C and 1200 °C. However, fewer than 95% of recrystallized grains recrystallized when the deformation temperature was lowered to 1000 °C. From the grain-boundary misorientation distribution in statically recrystallized samples, the fraction of high-angle grain boundaries decreased with an increasing deformation temperature from 1000 °C to 1200 °C for a given relaxation time. This was attributed to grain coarsening

  • 4.
    Al-Saadi, Munir
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. R&D, AB Sandvik Materials Technology, SE-811 81Sandviken, Sweden..
    Sandberg, Fredrik
    R&D, AB Sandvik Materials Technology, SE-811 81Sandviken, Sweden..
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Hulme-Smith, Christopher
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Influence of Strain Magnitude on Microstructure, Texture and Mechanical Properties of Alloy 825 during hot-forgingManuscript (preprint) (Other academic)
    Abstract [en]

    Alloy 825 is a nickel-base alloy that is common in applications with high stresses and corrosive environments. It is commonly processed by hot forging, but there are few data about how hot forging affects the microstructure, which is critical for both mechanical and corrosion performance. Here, the alloy was hot forged in a commercial thermomechanical process to three industrially-relevant strains and the microscture was examined using scanning electron microscopy and EBSD. The tensile properties were also measured after thermomechanical treatment. Dynamic recrystallization was prevalent during the process, so increasing the forging strain leads to smaller grains and also higher dislocation density. Data were combined to allow the 0.2% proof stress to be calculated as a function of forging strain. All forging strains were sufficient to meet the criteria of the relevant industrial standard for this material. The maximum yield strength and ultimate tensile strength were obtained after forging to a true strain of 0.9 were 413 MPa and 622 MPa, respecitvely, with a ductlity of 40%. This may be used to tailor thermomechanical treatments to achieve precise mechanical properties and serve as a basis for future studies into the corrosion performance of this alloy as a function of forging strain.

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  • 5.
    Safara Nosar, Nima
    et al.
    Dalarna University .
    Sandberg, Fredrik
    Sandvik Materials Technology, Storgatan 2, 81181 Sandviken, Sweden.
    Engberg, Göran
    Dalarna University.
    Characterization of Hot Deformation Behavior in a 13% Chromium Steel2018In: Proceedings of the THERMEC 2018, 2018Conference paper (Refereed)
    Abstract [en]

    The behavior of a 13% chromium steel subjected to hot deformation has been studied by performing hot compression tests in the temperature range of 850 to 12000C and at strain rates from 0.01 to 10 s-1. The uniaxial hot compression tests were performed on a Gleeble thermo-mechanical simulator. The best function that fits the peak stress for the material and its relation to the Zener-Hollomon parameter (Z) is derived. The average activation energy of this alloy in the entire test domain was found to be about 557 [kJmol-1] and the dynamic recrystallization (DRX) kinetics was studied to find the fraction DRX during deformation.

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  • 6.
    Sandberg, Fredrik
    Linnaeus University, School of Design, SE-39182 Kalmar, Sweden.
    Co-creating collaborative food serviceopportunities through work context maps2012In: ServDes. 2012 3rd Nordic Conference on Service Design and Service Innovation: CO-CREATING SERVICES / [ed] Päivi J. Tossavainen ; Milla Harjula ; Stefan Holmlid, Linköping, 2012, p. 243-251Conference paper (Refereed)
    Abstract [en]

    This paper presents a co-design workshop method where the participants use context maps of work activities as tools to visually explore collaborative service opportunities inside a food producer community. As an example the paper describes experiences from using the method together with small local food producers. During the workshop the food producers created and transferred knowledge regarding their work from the individual work maps to co-created future service maps. Although the food producers never had worked in these settings before,they had no problem sharing and co-creating complex work scenarios. The method uses both visual and verbal tools, which enables the participants to create a detailed service story as well as a visual overview. The use of the method encouraged the food producers to create service ideas, but it also started a dialog on how to bring the service concepts out to the real work context. The paper also reflects upon the method’s potential in supporting service designers.

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  • 7.
    Sandberg, Fredrik
    School of Design, Linnaeus University, Växjö, Sweden.
    Dead or alive: How municipalities can useservice design tools to create live servicesthat are flexible, mindful and involving2014In: ServDes.2014 Service Future; Proceedings of the fourth Service Design and Service Innovation Conference; Lancaster University; United Kingdom; 9-11 April 2014, Linköping, 2014, p. 434-439Conference paper (Refereed)
    Abstract [en]

    Regional service innovation is an emerging and important topic within the European Union. According to the OECD it is becoming ever more crucial for each European municipality to support collaborations between regional stakeholders in order to be innovative and competitive. But collaborations between large municipalities with fixed service routines and small flexible SMEs are challenging. In this paper we argue that service design and service designers’ knowledge about different techniques can act as a new approach for municipalities to interact with SMEs in a creative way. As an example of this; the paper describes experiences from a workshop where service designers; SMEs and Swedish municipalities prototypes a visual mapping activity. From this first pilot study we learned that visual mapping is an activity that makes it possible for municipalities to step out of their standardised service routines and step into a more involving and flexible service offering.

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  • 8.
    Sandberg, Fredrik
    LINNAEUS UNIVERSITY, SCHOOL OF DESIGN.
    VISUAL INQUIRY: A TOOL FOR PRESENTING AND SHARING CONTEXTUAL KNOWLEDGE2011In: Nordic Design Research Conference 2011, Making Design Matter, 2011Conference paper (Refereed)
    Abstract [en]

    This paper presents an inquiry method where the participants create a visual presentation of their experiential knowledge of working. As an example the paper describes experiences from using the inquiry method together with small local food producers. The owners use the visual inquiry tool to present their small company's activities, the stakeholders involved, problems, strengths,changes and dreams for the future. Although the food producers never had described their knowledge as one picture before, they had no problem mapping out and visually presenting complex information about their production. The method uses sticky notes as mapping tools, which enables the participants to rearrange information,point at related information, jump in time and also include the research group in the knowledge creation. The use of the visual inquiry method increases the participants’ involvement and community building. The paper also describes how the visual presentations, created at several inquiry sessions, are used in a workshop on collaborative services.

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  • 9.
    Sandberg, Fredrik
    et al.
    Linnaeus University, School of Design,SE-39182 Kalmar, Sweden.
    Westerlund, Bo
    Konstfack, LM Ericssons väg 14,Box 3601 Stockholm, Sweden.
    Widmark, Erik
    Transformator Design AB, Götgatan 19,11646 Stockholm, Sweden.
    Andersson, Sophie
    Transformator Design AB, Götgatan 19,11646 Stockholm, Sweden.
    The struggles of co-creation – The highs and lows of involving stakeholders into the service design process2013In: Collaborative Systems for Reindustrialization. 14th IFIP WG 5.5 Working Conference on Virtual Enterprises, PRO-VE 2013 Dresden, Germany, September/October 2013 Proceedings / [ed] Luis M. Camarinha-Matos ; Raimar J. Scherer, Heidelberg: Springer, 2013, p. 415-422Conference paper (Refereed)
    Abstract [en]

    This paper presents our experiences from a research project on how to co-develop new methods for idea generation within a service design practice. As an example the paper describes how service designers used two visual inquiry methods together with customers and employees in different service situations. The results show that that there is great potential in developing methods for co-design work based on design approaches. This project relies on a mindset where materials of different kinds, that can be organized and reorganized in different ways are used. This supports a way of creating knowledge that facilitates production of other results than the purely verbal. We have also realized that it requires a great amount of work to achieve a great result.

1 - 9 of 9
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