Change search
Refine search result
123 51 - 100 of 132
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 51.
    Fahlström, Karl
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. Swerea KIMAB, Joining Technology, Kista, Sweden .
    Andersson, Oscar
    Volvo Cars, Torslanda; XPRES, KTH Royal Institute of Technology.
    Todal, Urban
    Volvo Cars, Torslanda.
    Melander, Arne
    Swerea KIMAB, Joining Technology, Kista; XPRES, KTH Royal Institute of Technology, Stockholm.
    Minimization of distortions during laser welding of ultra-high strength steel2014In: ICALEO 2014 Congress proceedings, 2014, p. 1-10Conference paper (Refereed)
    Abstract [en]

    Ultra high strength steels are frequently used within the automotive industry for several components. Welding of these components is traditionally done by resistance spot welding, but to get further productivity and increased strength, laser welding has been introduced in the past decades. Fusion welding is known to cause distortions due to built-in stresses in the material. The distortions result in geometrical issues during assembly which become the origin of low joint quality due to gaps and misfits.

    U-beam structures of boron steel simulating B-pillars have been welded with laser along the flanges. Welding parameters and clamping have been varied to create different welding sequences and heat input generating a range of distortion levels. The distortions have been recorded dynamically with an optical measurement system during welding. In addition, final distortions have been measured by a digital Vernier caliper. The combined measurements give the possibility to evaluate development, occurrence and magnitude of distortions with high accuracy. Furthermore, section cuts have been analyzed to assess joint geometry and metallurgy.

    The results shows that final distortions appear in the range of 0-8 mm. Distortions occur mainly transversely and vertically along the profile. Variations in heat input show clear correlation with the magnitude of distortions and level of joint quality. A higher heat input in general generates a higher level of distortion with the same clamping conditions. Section cuts show that weld width and penetration are significantly affected by welding heat input.

    The present study identifies parameters which significantly influence the magnitude and distribution of distortions. Also, effective measures to minimize distortions and maintain or improve joint quality have been proposed.

    Finally, transient FE simulations have been presented which show the behavior of the profiles during the welding and unclamping process.

  • 52.
    Fargas, Gemma
    et al.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Universitat Politècnica de Catalunya, Barcelona, Spain.
    Roa, Joan Josep
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metallúrgica, Barcelona, Spain.
    Sefer, Birhan
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metallúrgica, Barcelona, Spain, Luleå University of Technology, Division of Materials Science, S-97187 Luleå, Sweden.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology.
    Antti, Marta Lena
    Luleå University of Technology, Division of Materials Science, S-97187 Luleå, Sweden.
    Mateo, Antonio M.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metallúrgica, Barcelona, Spain.
    Oxidation behavior of TI-6Al-4V alloy exposed to isothermal and cyclic thermal treatments2017In: Proceedings of the conference METAL 2017, TANGER Ltd. , 2017, p. 1573-1579Conference paper (Other academic)
    Abstract [en]

    One of the most common titanium alloys for aerospace industry is Ti-6Al-4V (usually designed as Ti-64) which is used for manufacturing aero-engine components, such as fan discs, compressor discs, blades andstators. The maximum service temperature for this alloy is limited partly because of degradation of mechanical properties at elevated temperatures (above 480 ºC). During the first stage of oxidation the oxidescale is protective, whereas after prolonged oxidation time it loses its protective nature and favours higher diffusion of oxygen through the oxide. In the present study, cyclic thermal treatments were performed in air at 500 and 700 ºC, up to 500 hours, and compared with similar studies carried out on isothermal oxidation conditions. The evolution of the surface oxidation was analyzed by metallographic techniques and X-ray diffraction, together with a detailed advanced characterization of the microstructure by Scanning Electron Microscopy and Focus Ions Beam. The results point out that the cyclic thermal treatments induced a strong increase of the weight gain compared to isothermal treatments. The analysis of the oxide scale revealed not only the presence of rutile, at 700 ºC, but also anatase and TiOx at 500 ºC for both isothermal and cyclic thermal treatments. At 700 ºC, thermal stress caused by cyclic thermal treatments promoted the fracture of the oxide after the first 20 hours.

  • 53.
    Fisk, Martin
    et al.
    Materials Science and Applied Mathematics, Malmö University.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes. GKN Aerospace Engine Systems, Trollhättan.
    du Rietz, Rickard
    Materials Science and Applied Mathematics, Malmö University.
    Haas, Sylvio
    MAX IV Laboratory, Lund University.
    Hall, Stephen
    Division of Solid Mechanics, Lund University.
    Precipitate evolution in the early stages of ageing in Inconel 718 investigated using small-angle x-ray scattering2014In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 612, p. 202-207Article in journal (Refereed)
    Abstract [en]

    Microstructural evolution during the early stages of ageing (less than one hour) in a Ni-Cr-Fe based superalloy Inconel 718 (IN718) has been investigated using Small-Angle X-ray Scattering (SAXS). The effects of precipitate kinetics on the precipitate size distribution are compared indirectly with SAXS measurements by using Vickers microhardness data. The microhardness increased after 4 min of ageing at a temperature of 760 degrees C, although the recorded SAXS data did not reveal the precipitate size distribution. This indicates that the precipitates had not evolved enough to be detected, but still a small number of precipitates increased the yield strength. After ageing the alloy for the shortest period for which data were available, 8 min, clear evidence of precipitates could be found from the SAXS data, showing that the gamma ‘’ - precipitates are about 6 nm in width and 3 nm in height. (C) 2014 Elsevier B.V. All rights reserved.

  • 54.
    Fisk, Martin
    et al.
    Malmö Högskola.
    Lundbäck, Andreas
    Luleå Tekniska Universitet.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Lindgren, Lars-Erik
    Luleå Tekniska Universitet.
    Finite Element Analysis Using a Dislocation Density Based Flow Stress Model Coupled with Model for Precipitate Evolution2014In: 8th International Symposium on Superalloy 718 and Derivatives / [ed] E. Ott, A. Banik, J. Andersson, I. Dempster, T. Gabb, J. Groh, K. Heck, R. Helmink, X. Liu och A. Wusatowska-Sarnek, John Wiley & Sons, 2014, p. 155-168Conference paper (Refereed)
  • 55.
    Fredriksson, Claes
    University West, Department of Engineering Science, Division of Industrial Engineering and Management, Electrical- and Mechanical Engineering. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. ANSYS - Education Division, University West, Trollhättan (SWE);Ansys Inc., Materials Business Unit, Education Division, Cambridge (GBR) .
    Integrating Materials and Manufacturing Education2021In: ASEE Annual Conference and Exposition, Conference Proceedings, American Society for Engineering Education , 2021Conference paper (Other academic)
    Abstract [en]

    The Material Science Tetrahedron, which is sometimes used to define the scope of this subject, connects the concepts of material processing, microstructure, material properties and performance of the material in applications. This model can be the foundation for discussing with students the impact of manufacturing processes to materials, such as heat treatments and consequences of welding or machining to the microstructure of metals as well as the effects of laser melting or sintering to additively manufactured (AM) components. On the other hand, it also indicates that material properties play an important role in determining manufacturing parameters, such as material removal rates or tool wear rates in machining. The EduPack educational software was developed as the first computer-based materials teaching resource at the Engineering department of Cambridge University. It consists of two linked databases - one of materials properties (MaterialUniverse) and one of manufacturing processes (ProcessUniverse). This is an ideal platform for cross-disciplinary teaching, not only for materials and manufacturing subjects, but the embedded tools also support all types of engineering design and product development courses; including materials and process selection as well as environmental and sustainability assessment of products. The two main databases contain around 4000 materials and 250 manufacturing processes, respectively, with informative images and schematics facilitating understanding. An extensive number of comparable properties are given in individual datasheets. All these properties are possible to visualize in colourful charts (Ashby charts) that provide good overviews and a good basis for understanding and decision-making. In this paper, relevant educational examples are shown that integrates materials with manufacturing in a natural way.

  • 56.
    Goel, Sneha
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Thermal post-treatment of Alloy 718 produced by electron beam melting2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Additive manufacturing (AM) has emerged as a disruptive technology and it is a vital part in the present era of fourth industrial revolution, Industry 4.0.Electron beam melting (EBM), a metal AM process, has received considerable industrial attention for near net shape manufacture of complex geometries with traditionally difficult-to-machine materials. EBM production of Alloy 718, a nickel-iron based superalloy possessing good mechanical and corrosion properties at elevated temperatures, is particularly promising for aerospace and energy sectors. However, EBM Alloy 718 builds are typically characterized by presence of inevitable defects and anisotropy, warranting post-processing thermal-treatments (post-treatments) to ensure that the components eventually meet the critical servicerequirements. The existing post-treatment standards include hot isostatic pressing (HIPing) over the temperature range of 1120°C-1185°C, followed by solution treatment (ST) and a two-step (‘8+8’ hours) aging under conditions conventionally adopted for cast and wrought Alloy 718, and no effort has yet been invested in optimizing post-treatment schedules specifically for EBM Alloy 718. Consequently, the objective of this work was to systematically investigate the response of EBM-built material to eachof the post-treatment steps to develop an improved understanding of howthe microstructure evolves with time during each step, since such knowledge can lay the foundation for optimizing the post-treatment protocol.Through study of microstructure and mechanical property assessment it was found that the temperature during HIPing can be reduced to 1120°C compared to the common practice employing higher temperatures. In addition, HIPing also caused complete dissolution of δ and γ"/γ' phases, promoted homogenization and resulted in drop in hardness but had no evident effect on the carbides and inclusions such as TiN and Al2O3 present in the as-built material. Subjecting EBM Alloy 718 to ST and two-step agingled to precipitation of δ phase and γ"/γ' phases, respectively.

    The evolution of microstructure during ST and two-step aging was also systematically investigated. Progressive precipitation and growth of grain boundary δ phase precipitates was observed during the entire 1 hour duration of ST, with samples not subjected to prior-HIPing exhibiting higher amount of the δ phase precipitation during ST. During the two-stepaging, detailed investigation of microstructure evolution and hardness changes showed that, particularly the conventional ‘8+8’ hour long two-stepaging treatment can be shortened to a ‘4+1’ hours treatment. Such shortened treatment was observed to be robust when applied to various kinds of EBM builds. Another approach for shortening post-treatment by integrating HIPing and HT inside the HIP vessel was also successfully implemented. These approaches with shortened post-treatment were also found to not compromise the mechanical response of EBM Alloy 718. Further shortening of the typical long thermal post-treatment cycle, through reduction in HIPing time from 4 hours to 1 hour and possible elimination of ST, also appears promising.

    Download full text (pdf)
    Spikblad
    Download full text (pdf)
    fulltext
  • 57.
    Goel, Sneha
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Mehtani, Hitesh
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, India (IND).
    Yao, Shu-Wei
    Xi’an Jiaotong University, School of Materials Science and Engineering, Xi’an, 710049, China (CHN).
    Samajdar, Indradev
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai, 400076, India (IND).
    Klement, Uta
    Chalmers University of Technology, Gothenburg, Sweden.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    As-Built and Post-treated Microstructures of an Electron Beam Melting (EBM) Produced Nickel-Based Superalloy2020In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 51, no 12, p. 6546-6559Article in journal (Refereed)
    Abstract [en]

    The microstructures of an electron beam melted (EBM) nickel-based superalloy (Alloy 718) were comprehensively investigated in as-built and post-treated conditions, with particular focus individually on the contour (outer periphery) and hatch (core) regions of the build. The hatch region exhibited columnar grains with strong texture in the build direction, while the contour region had a mix of columnar and equiaxed grains, with no preferred crystallographic texture. Both regions exhibited nearly identical hardness and carbide content. However, the contour region showed a higher number density of fine carbides compared to the hatch. The as-built material was subjected to two distinct post-treatments: (1) hot isostatic pressing (HIP) and (2) HIP plus heat treatment (HIP + HT), with the latter carried out as a single cycle inside the HIP vessel. Both post-treatments resulted in nearly an order of magnitude decrease in defect content in hatch and contour regions. HIP + HT led to grain coarsening in the contour, but did not alter the microstructure in the hatch region. Different factors that may be responsible for grain growth, such as grain size, grain orientation, grain boundary curvature and secondary phase particles, are discussed. The differences in carbide sizes in the hatch and contour regions appeared to decrease after post-treatment. After HIP + HT, similar higher hardness was observed in both the hatch and contour regions compared to the as-built material.

  • 58.
    Goel, Sneha
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Sittiho, Anumat
    University of Idaho, Department of Chemical and Materials Engineering, Moscow, ID 83844, United States.
    Charit, Indrajit
    University of Idaho, Department of Chemical and Materials Engineering, Moscow, ID 83844, United States.
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Effect of post-treatments under hot isostatic pressure on microstructural characteristics of EBM-built Alloy 7182019In: Additive Manufacturing, ISSN 2214-8604, E-ISSN 2214-7810, Vol. 28, p. 727-737Article in journal (Refereed)
    Abstract [en]

    Electron beam melting (EBM) has emerged as an important additive manufacturing technique. In this study, Alloy 718 produced by EBM was investigated in as-built and post-treated conditions for microstructural characteristics and hardness. The post-treatments investigated were hot isostatic pressing (HIP) and combined HIP + heat treatment (HIP + HT) carried out as a single cycle inside the HIP vessel. Both the post-treatments resulted in significant decrease in defects inevitably present in the as-built material. The columnar grain structure of the as-built material was found to be maintained after post-treatment, with some sporadic localized grain coarsening noted. Although HIP led to complete dissolution of δ and γ′′ phase, stable NbC and TiN (occasionally present) particles were observed in the post-treated specimens. Significant precipitation of γ′′ phase was observed after HIP + HT, which was attributed to the two-step aging heat treatment carried out during HIP + HT. The presence of γ′′ phase or otherwise was correlated to the hardness of the material. While the HIP treatment resulted in drop in hardness, HIP + HT led to 'recovery' of the hardness to values exceeding those exhibited by the as-built material. © 2019 Elsevier B.V.

  • 59.
    Guerrero Zuazo, David
    University West, Department of Engineering Science.
    Friction Stir Welding of Aluminium alloys for battery trays in EV’s2022Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Aluminium alloys are widely used in the industry of transportation, such as aerospace and automotive. With the current transformation from ICE power units to EV vehicles in the latest, the need of lightweight materials is increasing. Therefore, this project centres itself in investigating the possibility of using an aluminium alloy, AA6063 T6, to create the battery trays under the passengers in the new EV’s.

    To construct a battery tray, butt joints are needed for the base and cover and lap joint to attach both to the walls. This study examines both options with different welding parameters, with the objective of finding the best result for the automotive industry.

    In the case of the lap samples, HS-FSW is used to create different samples. Only six of those were deemed in a good state to be examined, defects and mechanical properties, such as hardness and tensile strength.

    On the other hand, the butt samples were welded in pairs and analysed following the same procedure as the butt samples. However, this part of the study was not completed and is left as future work.

    Concluding the study, a relation between the parameters and the obtained results was obtained, as well as defect free butt welds at high speed. This fulfils the possible needs of the industry, allowing an alternative and increasing productivity with HS-FSW methods. 

  • 60.
    Haas, Sylvio
    et al.
    Photon Science, DESY, Hamburg, Germany.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Fisk, Martin
    Malmö University, Materials Science and Applied Mathematics, Malmö, Sweden Division of Solid Mechanics, Lund University, Lund, Sweden.
    Park, Jun-Sang
    X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, USA.
    Lienert, Ulrich
    Photon Science, DESY, Hamburg, Germany.
    Correlation of precipitate evolution with Vickers hardness in Haynes® 282® superalloy: In-situ high-energy SAXS/WAXS investigation2018In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 11, p. 250-258Article in journal (Refereed)
    Abstract [en]

    The aim of this work is to characterize the precipitation kinetics in Haynes® 282® superalloys using in-situ high-energy Small Angle X-ray Scattering (SAXS) together with Wide Angle X-ray Scattering (WAXS). The phases identified by WAXS include γ (matrix), γ′ (hardening precipitates), MC (metallic carbides), and M23C6/M6C (secondary metallic carbides). The γ'-precipitates are spheroids with a diameter of several nanometres, depending on the temperature and ageing time. From the SAXS data, quantitative parameters such as volume fraction, number density and inter-particle distance were determined and correlated with ex-situ Vickers microhardness measurements. The strengthening components associated with precipitates and solid solutions are differentiated using the measured Vickers microhardness and SAXS model parameters. A square root dependence between strengthening attributable to the precipitates and the product of volume fraction and mean precipitate radius is found. The solid solution strengthening component correlates with the total volume fraction of precipitates.

  • 61.
    Hanning, Fabian
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    The Influence of Base Metal Microstructure on Weld Cracking in Manually GTA Repair Welded Cast ATI 718Plus®2018In: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications / [ed] Ott, E., Liu, X., Andersson, J., Bi, Z., Bockenstedt, K., Dempster, I., Groh, J., Heck, K., Jablonski, P., Kaplan, M., Nagahama, D. and Sudbrack, C., 2018, p. 917-928Conference paper (Refereed)
    Abstract [en]

    The effect of base metal conditions on the weld cracking response of cast ATI 718Plus® was investigated in this study, comparing as cast microstructure with pseudo hot isostatic pressing (HIP) heat treatments at 1120, 1160 and 1190 °C for dwell times of 4 and 24 h. Linear grooves have been filled using multipass manual gas tungsten arc welding (GTAW) to simulate repair welding conditions. Metallographic investigation revealed cracks in both base metal heat affected zone and fusion zone layers. The heat treatment temperatures chosen below, at and above incipient laves melting temperature of ATI 718Plus® were found to have an effect on weld cracking behaviour, with an increased average total crack length in the base metal heat affected zone for both 1160 and 1190 °C as compared to the as cast condition and the 1120 °C homogenization treatment. The increase in cracking susceptibility shows a correlation with the amount of Nb-rich secondary phases, with lower amounts leading to crack concentration to solidification grain boundaries present from the casting process, increasing the average crack length.

  • 62.
    Hanning, Fabian
    et al.
    Chalmers Univ Technol, Dept Ind & Mat Sci, Gothenburg, Sweden.
    Khan, Abdul Khaliq
    Univ Manitoba, Dept Mech Engn, Winnipeg, MB R3T 5V6, Canada.
    Steffenburg-Nordenstroem, Joachim
    GKN Aerosp Sweden AB, S-46138 Trollhattan, Sweden.
    Ojo, Olanrewaju
    Univ Manitoba, Dept Mech Engn, Winnipeg, MB R3T 5V6, Canada.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Investigation of the Effect of Short Exposure in the Temperature Range of 750-950 degrees C on the Ductility of Haynes (R) 282 (R) by Advanced Microstructural Characterization2019In: Metals, E-ISSN 2075-4701, Vol. 9, no 12, article id 1357Article in journal (Refereed)
    Abstract [en]

    A Gleeble-based test method has been developed to study the change in the ductility signature of Haynes (R) 282 (R) during isothermal exposure from 5 s to 1800 s. A temperature range of 750 to 950 degrees C has been used to investigate the effect of age-hardening reactions. Microstructural constituents have been analyzed and quantified using scanning and transmission electron microscopy. Carbides present in the material are identified as primary MC-type TiC carbides, Mo-rich M6C secondary carbides, and Cr-rich M23C6 secondary carbides. Gamma prime (gamma’) precipitates are present in all the material conditions with particle sizes ranging from 2.5 nm to 58 nm. Isothermal exposure causes the growth of gamma’ and development of a grain boundary carbide network. A ductility minimum is observed at 800-850 degrees C. The fracture mode is found to be dependent on the stroke rate, where a transition toward intergranular fracture is observed for stroke rates below 0.055 mm/s. Intergranular fracture is characterized by microvoids present on grain facets, while ductility did not change during ongoing age-hardening reactions for intergranularly fractured Haynes (R) 282 (R).

    Download full text (pdf)
    fulltext
  • 63.
    Hanning, Fabian
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Department of Industrial and Materials Science, Chalmers University of Technology, Gothenburg.
    Singh, Gurdit
    University West, Department of Engineering Science.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    The Effect of Grain Size on theSusceptibility Towards Strain Age Crackingof Wrought Haynes® 282®2020In: SPS 2020: Proceedings of the Swedish Production Symposium / [ed] Kristina Säfsten & Fredrik Elgh, Amsterdam: IOS Press, 2020, p. 407-416Conference paper (Other academic)
    Abstract [en]

    The effect of grain size on the suceptibility towards strain age cracking (SAC) has been investigated for Haynes® 282® in the tempeature range of 750 to 950°C after isothermal exposure up to 1800s. Grain growth was induced by heattreating the material at 1150°C for 2h, resulting in a fourfold increase in grain size. Hardness was significanlty reduced after heat treatment as compared to millannealed material. Large grain size resulted in intergranular fracture over a widertemperature range than small grain size material. Ductility was lowest at 850°C, while lower values were observed to be correlated to increased grain size. The rapid formation of grain boundary carbide networks in Haynes® 282® is found to be notable to compensate for higher local stresses on grain boundaries due to incresedgrain size. 

    Download full text (pdf)
    fulltext
  • 64.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Charles, Corinne
    University West, Department of Engineering Science, Division of Production Engineering. University West, Department of Engineering Science, Division of Welding Technology.
    Dzevad, Imamovic
    Volvo Aero Coorporation.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    Dep of signal and systems, Chalmers.
    Towards stable high-speed metal-wire deposition, Part I: Parameter studyIn: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387Article in journal (Refereed)
  • 65.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Production Engineering.
    Ottosson, Mattias
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    Chalmers.
    Control Design for Automation of Robotized Laser Metal-Wire Deposition2008In: Proceedings of the 17th IFAC World Congress, International Federation of Automatic Control , 2008, p. 14785-14791Conference paper (Other academic)
    Abstract [en]

    In this paper a novel approach towards automation of robotized laser metal-wire deposition (RLMwD) is described. The RLMwD technique is being developed at University West in cooperation with Swedish industry for solid freeform fabrication of fully dense metal structures. The process utilizes robotized fibre laser welding and metal wire filler material, together with a layered manufacturing method, to create metal structures directly from a CAD drawing. The RLMwD process can also be used for repair or modification of existing components. This paper faces the challenge of designing a control system for maintaining stable process variables, such as a constant layer height and a stable component temperature, during the entire manufacturing process. Several problems are identified and discussed in the paper, e.g. the difficulty of obtaining the bead height in the weld pool environment. The case study is a repair application for stamping tools, where worn out trim edges are to be repaired. Issues regarding the control design, system identification, and the practical implementation of this application are discussed.

  • 66.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Ottosson, Mattias
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Production Engineering.
    Kristiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Visual feed-back for operator interaction in robotized laser metal deposition2008In: Proceedings of the 22nd International Conference on Surface Modification Technologies SMT22: Held at University West, Trollhättan, Sweden September 22-24, 2008 / [ed] T.S. Sudarshan & Per Nylen, 2008, p. 297-304Conference paper (Other academic)
  • 67.
    Holmberg, Jonas
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Swerea Group.
    Palosaari, Mikko
    Outokumpu Stainless Oy, Stresstech OY.
    Hosseini, Seyed
    Islamic Azad University, Swerea Group.
    Larjosuo, Henri
    Stresstech OY.
    Andersson, Pär Yngve
    Chalmers University of Technology, Orebro University Swerea Group.
    Round Robin Study on Residual Stresses Using X-Ray Diffraction for Shot-Peened Tool Steel Specimens2018In: Residual Stresses 2018, Ecrs-10, Millersville, PA, USA: MATERIALS RESEARCH FORUM LLC , 2018, Vol. 6, p. 51-56Conference paper (Refereed)
    Abstract [en]

    Residual stress measurements using x-ray diffraction is a well established method used within the industrial and academic community to verify the performance of different processes for metallic materials. The measurement gives an absolute value of the stress state which can be used to design and optimize the process route to induce beneficial compressive residual stresses and avoid detrimental tensile stresses. Investigating the uncertainty and accuracy of the measurement system, operator and the material is therefore of high relevance both from an industrial and scientific point of view. Round robin testing is an important way to quantify the uncertainties that could affect the quality of the measured results and hence how a process is optimized and tuned. Such an investigation allows the operator to understand and reduce variations. Current round robin test includes results from five different laboratories using comparable equipments located in Sweden, Finland, Germany and United States. This work focuses on five shot-peened tool steel specimens produced with identical process settings. Additionally, an investigation of the repeatability of the system, influence of the operator, variations within the specimen, and the long time stability of the specimens has been measured.

  • 68.
    Holmberg, Jonas
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. RISE IVF AB, Argongatan 30, Mölndal, 431 53, Sweden.
    Wretland, Anders
    GKN Aerospace Sweden AB, Trollhättan, 461 81, Sweden.
    Berglund, Johan
    RISE IVF AB, Argongatan 30, Mölndal, 431 53, Sweden.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Selection of milling strategy based on surface integrity investigations of highly deformed Alloy 718 after ceramic and cemented carbide milling2020In: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 58, p. 193-207Article in journal (Refereed)
    Abstract [en]

    High speed milling with ceramic indexable inserts is a current practice for manufacturing of gas turbine components in superalloys since it allows for high material removal rates. Ceramic milling is used for rough milling, which is followed by cemented carbide semi- and finish milling. The tool motion play an important role on the resulting surface integrity. The machining strategy of up or down milling will induce different degree of residual stresses and deformations. Increased knowledge of selecting the machining strategy with lowest impact will promote improved productivity by using ceramic milling to a greater extent based on the affected depth. The main objective in this work has been to correlate the residual stresses and deformations to promote a greater utilization of ceramic milling while still producing surfaces with acceptable properties. Prior investigations have shown that ceramic milling induce very high tensile stresses in the surface, exceeding the material’s nominal yield strength. A second objective has been to explain these stress levels by thorough investigations of the deformation after milling. In this study, milling tests with new and worn ceramic and cemented carbide inserts have been performed in Alloy 718. The topography, residual stresses, deformation and hardness have been investigated for up, centre and down milling. Residual stress measurements were performed using X-ray diffraction, followed by evaluation of hardness and deformation, using hardness testing, light optical microscopy as well as electron back scattering diffraction (EBSD). These results have been used to determine an appropriate milling strategy based on lowest possible impact in respect to residual stresses and deformation. The results show a high degree of deformation after milling that differs for the up, centre and down milling. Based on these results, it is shown that up milling is preferable for new inserts but as the inserts wear out, down milling becomes more suitable since a lower degree of deformation and residual stress impact was observed. EBSD and hardness testing showed that the milling, especially ceramic milling, caused severe deformation of the surfaces resulting in grain refinement to a nano-crystalline level. This is most likely the explanation for the prevalence of the high tensile stresses without distorting or causing failure. © 2020 The Authors

  • 69.
    Hosseini, S.B.
    et al.
    Chalmers University of Technology, Department of Materials and Manufacturing Technology.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Production Engineering. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Johansson, S
    Lektronik, Ing.f:a, 424 49 Angered, Sweden .
    Klement, Uta
    Chalmers University of Technology, Department of Materials and Manufacturing Technology.
    Kaminski, J
    Chalmers University of Technology, Department of Materials and Manufacturing Technology.
    Ryttberg, K.
    AB SKF, 415 50 Gothenburg.
    Cutting temperatures during hard turning: Measurements and effects on white layer formation in AISI 521002014In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 214, no 6, p. 1293-1300Article in journal (Refereed)
    Abstract [en]

    This paper concerns the temperature evolution during white layer formation induced by hard turning of martensitic and bainitic hardened AISI 52100 steel, as well as the effects of cutting temperatures and surface cooling rates on the microstructure and properties of the induced white layers. The cutting temperatures were measured using a high speed two-colour pyrometer, equipped with an optical fibre allowing for temperature measurements at the cutting edge. Depending on the machining conditions, white layers were shown to have formed both above and well below the parent austenitic transformation temperature, Ac1, of about 750 C. Thus at least two different mechanisms, phase transformation above the Ac1 (thermally) and severe plastic deformation below the Ac1 (mechanically), have been active during white layer formation. In the case of the predominantly thermally induced white layers, the cutting temperatures were above 900 C, while for the predominantly mechanically induced white layers the cutting temperatures were approximately 550 C. The surface cooling rates during hard turning were shown to be as high as 104-105 C/s for cutting speeds between 30 and 260 m/min independent of whether the studied microstructure was martensitic or bainitic. Adding the results from the cutting temperature measurements to previous results on the retained austenite contents and residual stresses of the white layers, it can be summarised that thermally induced white layers contain significantly higher amounts of retained austenite compared to the unaffected material and display high tensile residual stresses. On the contrary, in the case of white layers formed mainly due to severe plastic deformation, no retained austenite could be measured and the surface and subsurface residual stresses were compressive. © 2014 Elsevier B.V.

  • 70.
    Hosseini, Vahid A.
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Aashuri, H.
    Materials Science and Engineering Dep., Sharif University of Technology, Tehran, Iran.
    Kokabi, A. H.
    Materials Science and Engineering Dep., Sharif University of Technology, Tehran, Iran.
    Study of the effect of tool geometry on semisolid stir welding of a AZ91 magnesium alloy2015In: Proceedings of the 18th International Conference on Joining Materials, JOM-Institute , 2015, p. 1-10Conference paper (Refereed)
    Abstract [en]

    Semisolid stir welding is a newly developed method suitable for joining of the magnesium alloy AZ91. In this study, the effect of tool geometries on the joint properties such as bending strength and the occurrence of porosity are studied. A 2 mm-thick Mg-25%Zn interlayer was placed between two AZ91 plates and the plate was heated up to 530°C before joining. At this temperature, when both the interlayer and the base metal were in the semisolid state, a stirrer was introduced into the joint. Drill-tip and round shape stirrer tools were employed at three different stirring rates. Welds produced with the two methods showed similar properties in the shear punch test. However, using the round tool geometry resulted in welds with excellent bending strength closely matching that of the base metal especially at the highest stirring rate. The improved properties when using the round tool was a result of the formation of a very fine and uniform microstructure with a low content of porosity.

  • 71.
    Hosseini, Vahid
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Welding Technology.
    Gonzalez, Daniel
    Bodycote, Surahammar (SWE).
    Oliver, James
    Outokumpu Stainless AB, Avesta (SWE).
    Folkeson, Nicklas
    ESAB AB, Göteborg (SWE).
    Thuvander, Mattias
    Department of Physics, Chalmers University of Technology, Gothenburg, (SWE).
    Lindgren, Kristina
    Department of Physics, Chalmers University of Technology, SE-412 96 Gothenburg (SWE).
    Karlsson, Leif
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Welding Technology.
    Precipitation kinetics of Cu-rich particles in super duplex stainless steels2021In: Journal of Materials Research and Technology, ISSN 2238-7854, Vol. 15, p. 3951-3964Article in journal (Refereed)
    Abstract [en]

    Complex precipitation behavior of Cu-rich particles (CRPs) was investigated and simulated in continuously cooled and quench-aged super duplex stainless steel. Atom probe tomography (APT) and scanning electron microscopy showed that slow cooling resulted in nonuniform multimodal CRP precipitation and spinodal decomposition, while in the fast cooled and quench-aged conditions, more uniform precipitation of CRPs with no visible spinodal decomposition was found. Depletion of Cu, Ni, and Mn was observed in the ferrite next to the CRPs during growth, but not during dissolution. Some evidence of Ostwald ripening was seen after slow cooling, but in the quench-aged condition, particle coalescence was observed. Large CRPs disappeared next to a ferrite–austenite phase boundary after slow cooling when Cu was depleted due to the diffusion to austenite as also predicted by moving boundary Dictra simulation. Comparing Cu depleted areas next to CRPs analyzed by APT and moving boundary Dictra simulation of CRP–ferrite showed that the effective Cu diffusion coefficient during the early-stage precipitation was about 300 times higher than the Cu diffusion coefficient in ferrite at 475 °C. Using the effective diffusion coefficient and a size-dependent interfacial energy equation, CRP size distribution was successfully predicted by the Langer–Schwartz model implemented in Thermo-Calc Prisma. Applying a short aging time and continuous cooling increased the hardness and decreased the toughness values compared to the solution annealed condition. A nonuniform distribution of Cu in ferrite, the duplex structure, and partitioning of alloying elements among different phases are factors making CRP precipitation in duplex stainless steels complex.

    Download full text (pdf)
    JMR&T
  • 72.
    Hosseini, Vahid
    et al.
    University West, Department of Engineering Science, Division of Welding Technology. Hogskolan Vast.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Welding Technology.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Welding Technology.
    Effect of multipass TIG welding on the corrosion resistance and microstructure of a super duplex stainless steel2017In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 68, no 4, p. 405-415Article in journal (Refereed)
    Abstract [en]

    This is a study of the effect of repetitive TIG (tungsten inert gas) welding passes, melting and remelting the same material volume on microstructure and corrosion resistance of 2507 (EN 1.4410) super duplex stainless steel. One to four weld passes were autogenously (no filler added) applied on a plate using two different arc energies and with pure argon shielding gas. Sensitization testing showed that multipass remelting resulted in significant loss of corrosion resistance of the weld metal, in base material next to the fusion boundary, and in a zone 1 to 4 mm from the fusion boundary. Metallography revealed the main reasons for sensitization to be a ferrite-rich weld metal and precipitation of nitrides in the weld metal, and adjacent heat affected zone together with sigma phase formation at some distance from the fusion boundary. Corrosion properties cannot be significantly restored by a post weld heat treatment. Using filler metals with higher nickel contents and nitrogen containing shielding gases, are therefore, recommended. Welding with a higher heat input and fewer passes, in some cases, can also decrease the risk of formation of secondary phases and possible corrosion attack.

  • 73.
    Hosseini, Vahid
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Thuvander, Mattias
    Department of Physics, Chalmers University of Technology, Gothenburg (SWE).
    Lindgren, K.
    Department of Physics, Chalmers University of Technology, Gothenburg (SWE).
    Oliver, James
    Outokumpu Stainless AB, Avesta (SWE).
    Folkeson, Nicklas
    ESAB AB, SE-417 55 Gothenburg (SWE).
    Gonzalez, Daniel
    Bodycote, Surahammar (SWE).
    Karlsson, Leif
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Welding Technology.
    Fe and Cr phase separation in super and hyper duplex stainless steel plates and welds after very short aging times2021In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 210, article id 110055Article in journal (Refereed)
    Abstract [en]

    Fe and Cr phase separation in ferrite, causing 475°C-embrittlement, was studied after very short aging times in super duplex stainless steel (SDSS) and hyper duplex stainless steel (HDSS) plates and welds. Atom probe tomography showed that hot-rolled SDSS, experiencing significant metal working, had faster kinetics of phase separations compared to the SDSS and HDSS welds after 5 min aging at 475 °C. The surface of the 33-mm SDSS plate had faster Fe and Cr phase separation and larger toughness drop. A higher density of dislocations next to the austenite phase boundary in ferrite, detected by electron channeling contrast, can promote the phase separation at the surface of the plate with lower austenite spacing. The toughness dropped in HDSS welds after aging, but SDSS welds maintained their toughness. An inverse simulation method considering an initial sinusoidal nanometric Cr and Fe fluctuation showed that Ni increases the interdiffusion of Cr in the system, resulting a higher degree of phase separation in SDSS welds than the HDSS weld. Within the composition range of the studied SDSS and HDSS materials, the processing influences the Fe and Cr phase separation more than the variation in composition during short aging or typical fabrication times. 

    Download full text (pdf)
    Materials & Design
  • 74.
    Jafari, R.
    et al.
    Department of Material Science and Engineering, Tarbiat Modares University, Tehran, Iran.
    Sadeghimeresht, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Shahrabi Farahani, T.
    Department of Material Science and Engineering, Tarbiat Modares University, Tehran, Iran .
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    KCl-induced corrosion behavior of HVAF-sprayed Ni-based coatings in ambient air2017Conference paper (Other academic)
  • 75.
    Jafari, Reza
    et al.
    Tarbiat Modares University, Department of Material Science and Engineering, Tehran, Iran.
    Sadeghimeresht, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Shahrabi Farahani, Taghi
    Tarbiat Modares University, Department of Material Science and Engineering, Tehran, Iran.
    Huhtakangas, Matti
    M. H. Engineering AB, Karlskoga, Sweden .
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    KCl-Induced High Temperature Corrosion Behavior of HVAF-Sprayed Ni-Based Coatings in Ambient Air2018In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, no 3, p. 500-511Article in journal (Refereed)
    Abstract [en]

    KCl-induced high temperature corrosion behavior of four HVAF-sprayed Ni-based coatings (Ni21Cr, Ni5Al, Ni21Cr7Al1Y, and Ni21Cr9Mo) under KCl deposit has been investigated in ambient air at 600°C up to 168h. The coatings were deposited onto 16Mo3 steel - a widely used boiler tube material.Uncoated substrate, 304L and Sanicro25 were used as reference materials in the test environment.SEM/EDS and XRD techniques were utilized to characterize the as-sprayed and exposed samples.The results showed that the small addition of KCl significantly accelerated degradation to the coatings. All coatings provided better corrosion resistance compared to the reference materials. The alumina-forming Ni5Al coating under KCl deposit was capable of forming a more protective oxide scale compared to the chromia-forming coatings as penetration of Cl through diffusion paths was hindered. Both active corrosion and chromate formation mechanisms were found to be responsible for Page 1 of 23ASM the corrosion damages. The corrosion resistance of the coatings based on the microstructure analysis and kinetics had the following ranking (from the best to worst): Ni5Al >Ni21Cr> Ni21Cr7Al1Y>Ni21Cr9Mo.

    Download full text (pdf)
    fulltext
  • 76.
    Jiang, Janna
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Fasth, Angelica
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylen, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Choi, W.B.
    Center for Thermal Spray Research, Stony Brook, NY, USA.
    Microindentation and Inverse Analysis to Characterize Elastic-Plastic Properties for Thermal Sprayed Ti2AlC and NiCoCrAlY2009In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 18, no 2, p. 194-200Article in journal (Refereed)
    Abstract [en]

    Elastic-plastic material properties for HVOF sprayed Ti2AlC (sprayed with Maxthal 211 powder) and plasma sprayed NiCoCrAlY coatings were investigated using modeling and experimental Berkovich microindentation. Optical microstructure evaluations were also performed. The theories of Hertz, Oliver and Pharr were combined with finite element analysis for extracting the material properties. Empirically based material models for both thermal sprayed Ti2AlC and NiCoCrAlY coatings are proposed.

  • 77.
    Jiang, Janna
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Numerical modelling of the compression behaviour of single-crystalline MAX-phase materials2010In: Advanced materials research, ISSN 1022-6680, Vol. 89-91, p. 262-267Article in journal (Refereed)
    Abstract [en]

    In this article a numerical model to describe the mechanical behaviour of nanophased singlecrystalline Ti3SiC2 is proposed. The approach is a two dimensional finite element periodic unit cell consisting of an elastic matrix interlayered with shear deformable slip planes which obey the Hill's yield criterion. The periodic unit cell is used to predict compression material behaviour of Ti3SiC2 crystals with arbitrary slip plane orientations. Stress strain relationships are derived for Ti 3SiC2, and the effect of slip plane volume fraction as well as orientation of the slip planes are investigated. The two main deformation mechanisms of the material namely; ordinary slip and so called kinking are considered in the study.

  • 78.
    Jothi, Sathiskumar
    et al.
    Swansea University Bay Campus, College of Engineering, Engineering East Building, Fabian Way, Swansea, United Kingdom.
    Merzlikin, S.V.
    Max-Planck-InstitutfürEisenforschung GmbH, Max-Planck-Strae 1, Düsseldorf, Germany.
    Croft, T.N.
    Swansea University Bay Campus, College of Engineering, Engineering East Building, Fabian Way, Swansea, United Kingdom.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Brown, S.G.R.
    Swansea University Bay Campus, College of Engineering, Engineering East Building, Fabian Way, Swansea, United Kingdom.
    An investigation of micro-mechanisms in hydrogen induced cracking in nickel-based superalloy 7182016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 664, p. 664-681Article in journal (Refereed)
    Abstract [en]

    Hydrogen embrittlement of the nickel-iron based superalloy 718 has been investigated using slow strain rate tests for pre-charged material and also in-situ hydrogen charging during testing. Fractography analyses have been carried using scanning electron microscopy, electron back-scattering diffraction and orientation image microscopy concentrating on the influence of microstructural features and associated micro-mechanisms leading to hydrogen induced cracking and embrittlement. It was observed that hydrogen induced transgranular cracking initiates at micro-voids in the crystal lattice. Similar behaviour has been observed in multi-scale finite element chemo-mechanical numerical simulations. In contrast, hydrogen induced localized slip intergranular cracking was associated with the formation of micro-voids in intergranular regions. The effects of grain boundary and triple junction character on intergranular hydrogen embrittlement were also investigated. It was observed that low end high angle misorientations (LHAM), 15°<Ξ ≀ 35°, and critical high angle misorientations (CHAM), 35° < 50°, are preferential sites for hydrogen induced cracking. In contrast, few or no hydrogen induced cracks were observed at low angle misorientations (LAM), 0°≀ Ξ le; 15°, high end high angle misorientations (HHAM), 50°<Ξ ≀ 55°, or special GB misorientations (SGB), Ξ > 55°. Finally, the use of grain boundary engineering techniques to increase the resistance of super alloy 718 to hydrogen induced cracking and embrittlement is discussed. © 2016 Elsevier B.V. All rights reserved.

  • 79.
    Kanhed, Satish
    et al.
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Awasthi, Shikha
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Midha, Swati
    Department of Textile Technology Indian Institute of Technology Delhi New Delhi, 110016, India.
    Nair, Jitin
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Nisar, Ambreen
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Patel, Anup Kumar
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Pandey, Aditi
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Sharma, Rajeev
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Goel, Sneha
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Upadhyaya, Anish
    Powder Metallurgy Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Ghosh, Sourabh
    Department of Textile Technology Indian Institute of Technology Delhi New Delhi, 110016, India.
    Balani, Kantesh
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Microporous Hydroxyapatite Ceramic Composites as Tissue Engineering Scaffolds: An Experimental and Computational Study2018In: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 20, no 7, article id 1701062Article in journal (Refereed)
    Abstract [en]

    Bone‐tissue engineering mandates the development of multi‐functional bioactive porous hydroxyapatite (HAp) scaffolds. Herein, microwave sintered HAp/ZnO and HAp/Ag composite scaffolds with ≈5–19% porosity are developed using 0–30 vol% graphite as a porogen. The mechanical properties of the porous scaffold are analyzed in detail, revealing that even being more porous, the reinforcement of ZnO (9% porosity, hardness of 2.8 GPa, and toughness of 3.5 MPa.m1/2) has shown to have better hardness and fracture toughness when compared to Ag (5% porosity, hardness of 1.6 GPa, and toughness of 2.6 MPa.m1/2). The flexural strength obtained experimentally are complemented with a finite‐element technique that adopts microstructural features in visualizing the effect of porosity on stress distribution. The antibacterial efficacy and cytocompatibility of these composites are validated by increased metabolic activity and conspicuous cell‐matrix interactions. The anticipation of the results reveal that HAp/ZnO (9% porosity) and HAp/Ag (5% porosity) composites can be used as a potential multi‐functional bone implant scaffolds.

  • 80.
    Karimi Neghlani, Paria
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Deng, Dunyong
    Linköping University, Division of Engineering Materials, Linköping, Sweden.
    Sadeghimeresht, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Olsson, Jonas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Ålgårdh, Joakim
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Swerea KIMAB AB, Kista, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Microstructure Development in Track-by-Track Melting of EBM-Manufactured Alloy 7182018In: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications / [ed] Ott, E., Liu, X., Andersson, J., Bi, Z., Bockenstedt, K., Dempster, I., Groh, J., Heck, K., Jablonski, P., Kaplan, M., Nagahama, D. and Sudbrack, C., Springer, 2018, p. 643-654Conference paper (Refereed)
    Abstract [en]

    Electron beam melting (EBM) is a powder-bed fusion process within the group of additive manufacturing (AM) technology that is used to fabricate high performance metallic parts. Nickel-Iron base superalloys, such as Alloy 718, are subjected to successive heating and cooling at temperatures in excess of 800 °C during the EBM process. Characterization of the dendritic structure, carbides, Laves and δ-phase were of particular interest in this study. These successive thermal cycles influence the microstructure of the material resulting in a heterogeneous structure, especially in the building direction. Hence, the aim of this study was to gain increased fundamental understanding of the relationship between the processing history and the microstructure formed within a single layer. Different numbers of tracks with equal heights were for this purpose produced, varying from one to ten tracks. All tracks used the same process parameters regardless of number and/or position. Microstructure characteristics (sub-grain structure, grain structure and phases) were analyzed by optical microscopy, scanning electron microscopy equipped with energy disperse spectroscopy and electron backscatter diffraction. The direction of dendrites changed in the overlap zones within the tracks due to re-melting of material in the overlap zone. The primary dendrite arm spacings slightly increased along multi-tracks owing to a slight decrease in cooling rate by addition of the next tracks. Epitaxial growth of grains were observed in all samples due to partial re-melting of grains in previous layers and surface nucleation was also found to occur in all tracks.

  • 81.
    Karimi Neghlani, Paria
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Sadeghi, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Ålgårdh, Joakim
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. GE Additive | Arcam EBM, Mölnlycke (SWE).
    Keshavarzkermani, Ali
    Multi‑Scale Additive Manufacturing Lab, Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo (CAN).
    Esmaeilizadeh, Reza
    Multi‑Scale Additive Manufacturing Lab, Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo (CAN).
    Toyserkani, Ehsan
    Multi‑Scale Additive Manufacturing Lab, Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo (CAN).
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Columnar-to-equiaxed grain transition in powder bed fusion via mimicking casting solidification and promoting in situ recrystallization2021In: Additive Manufacturing, ISSN 2214-8604, E-ISSN 2214-7810, Vol. 46, article id 102086Article in journal (Refereed)
    Abstract [en]

    Columnar grain structure typically formed along the build direction in the electron beam-powder bed fusion (EBPBF) technique leads to anisotropic physical and mechanical properties. In this study, casting solidification condition was mimicked, and in situ recrystallization was promoted in EB-PBF to facilitate columnar-to-equiaxed grain structure transition in Alloy 718. This is achieved via a unique linear melting strategy coupled with a specific selection of process parameters in EB-PBF. It was found that site-specific melting using line order number (LON) function affected the cooling rate and temperature gradient, which controlled grain morphology and texture. A high LON resulted in a large equiaxed grain zone with a random texture, whereas a fixed LON with a high areal energy density led to a strong texture. The main driving force in the formation of cracks and shrinkage defects during the transition was investigated. A high LON at a fixed areal energy density reduced the average total shrinkage defects and crack length. The hardness was decreased through the transition, which was linked to the reduction in the size of the gamma ‘’ precipitates.

    Download full text (pdf)
    Additive Manufacturing
  • 82.
    Karimi Neghlani, Paria
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Sadeghi, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Ålgårdh, Joakim
    Arcam-EBM (a GE Additive), 435 33, Mölnlycke (SWE).
    Olsson, Jonas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Hörnqvist Colliander, Magnus
    Department of Applied Physics, Chalmers University of Technology, Gothenburg (SWE).
    Harlin, Peter
    Sandvik Additive Manufacturing, Sandviken (SWE).
    Toyserkani, Ehsan
    Department of Mechanical and Mechatronic Engineering, Waterloo University, Waterloo (CAN).
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Tailored grain morphology via a unique melting strategy in electron beam-powder bed fusion2021In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 824, article id 141820Article in journal (Refereed)
    Abstract [en]

    This study presents a unique melting strategy in electron beam-powder bed fusion of Alloy 718 to tailor the grain morphology from the typical columnar to equiaxed morphology. For this transition, a specific combination of certain process parameters, including low scanning speeds (400-800 mm/s), wide line offsets (300-500 mu m) and a high number of line order (#10) was selected to control local solidification conditions in each melt pool during the process. In addition, secondary melting of each layer with a 90. rotation with respect to primary melting induced more vigorous motions within the melt pools and extensive changes in thermal gradient direction, facilitating grain morphology tailoring. Four different types of microstructures were classified according to the produced grain morphology depending on the overlap zone between two adjacent melt pools, i.e., fully-columnar (overlap above 40 %), fully-equiaxed (overlap below 15 %), mixed columnar-equiaxed grains, and hemispherical melt pools containing mixed columnar-equiaxed grains (overlap similar to 20-25 %). The typical texture was <001>; however, the texture was reduced significantly through the transition from the columnar to equiaxed grain morphology. Along with all four different microstructures, shrinkage defects and cracks were also identified which amount of them reduced by a reduction in areal energy input. The hardness was increased through the transition, which was linked to the growth of the.” precipitates and high grain boundary density in the fully-equiaxed grain morphology.

    Download full text (pdf)
    Materials Science & Engineering A
  • 83.
    Karimi Neghlani, Paria
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Sadeghimeresht, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Åkerfeldt, Pia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Luleå, 971 87, Sweden.
    Ålgårdh, Joakim
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Powder Materials & Additive Manufacturing, Swerea KIMAB AB, Kista, 164 40, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Influence of successive thermal cycling on microstructure evolution of EBM-manufactured alloy 718 in track-by-track and layer-by-layer design2018In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 160, p. 427-441Article in journal (Refereed)
    Abstract [en]

    Successive thermal cycling (STC) during multi-track and multi-layer manufacturing of Alloy 718 using electron beam melting (EBM) process leads to a microstructure with a high degree of complexity. In the present study, a detailed microstructural study of EBM-manufactured Alloy 718 was conducted by producing samples in shapes from one single track and single wall to 3D samples with maximum 10 longitudinal tracks and 50 vertical layers. The relationship between STC, solidification microstructure, interdendritic segregation, phase precipitation (MC, δ-phase), and hardness was investigated. Cooling rates (liquid-to-solid and solid-to-solid state) was estimated by measuring primary dendrite arm spacing (PDAS) and showed an increased cooling rate at the bottom compared to the top of the multi-layer samples. Thus, microstructure gradient was identified along the build direction. Moreover, extensive formation of solidification micro-constituents including MC-type carbides, induced by micro-segregation, was observed in all the samples. The electron backscatter diffraction (EBSD) technique showed a high textured structure in 〈001〉 direction with a few grains misoriented at the surface of all samples. Finer microstructure and possibility of more γ″ phase precipitation at the bottom of the samples resulted in slightly higher (~11%) hardness values compared to top of the samples. © 2018 Elsevier Ltd

  • 84.
    Karlsson, Leif
    et al.
    University West, Department of Engineering Science, Divison of Natural Sciences, Surveying and Mechanical Engineering.
    Börjesson, J.
    ESAB AB, PO Box 8004, Göteborg.
    Orientation relationships of intragranular austenite in duplex stainless steel weld metals2014In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 19, no 4, p. 318-323Article in journal (Refereed)
    Abstract [en]

    Formation and characteristics of fine intragranular austenite were studied for low energy input duplex stainless steel welds. Microstructures were largely ferritic with some allotriomorphic grain boundary austenite, Widmanstätten type austenite, fine intragranular austenite and nitrides. Electron backscattered diffraction analysis revealed that grain boundary austenite had a random orientation relationship (OR) with one of the adjacent ferrite grains and was close to Kurdjumov-Sachs (KS) with the other, whereas Widmanstätten austenite always showed an OR near KS. The finest intragranular austenite was mainly randomly oriented, whereas coarser austenite more often was close to KS. It is argued that the OR of intragranular austenite with the ferritic matrix is governed by a combination of composition, determining driving force for nucleation at temperature, cooling rate and the availability of nitrides acting as nucleation sites. A random OR is most likely for higher cooling rates and compositions promoting nucleation at lower temperatures. © 2014 Institute of Materials, Minerals and Mining.

  • 85.
    Kisielewicz, Agnieszka
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    Sadeghi, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Production Systems.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Production Systems.
    Palumbo, Gianfranco
    CNR-IFN Institute for Photonics and Nanotechnologies, Physics Department, Bari, Italy (ITA).
    Ancona, Antonio
    University West, Department of Engineering Science, Division of Production Systems. CNR-IFN Institute for Photonics and Nanotechnologies, Physics Department, Bari, Italy (ITA).
    In-process spectroscopic detection of chromium loss during Directed Energy Deposition of alloy 7182020In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 186, article id 108317Article in journal (Refereed)
    Abstract [en]

    In this work, a fast optical spectrometer was used to monitor the Directed Energy Deposition (DED) process, during the deposition of Alloy 718 samples with different laser power, thus different energy inputs into the material. Spectroscopic measurements revealed the presence of excited Cr I atoms in the plasma plume. The presence was more apparent for the samples characterized by higher energy input. The Cr depletion from these samples was confirmed by lower Cr content detected by Energy-Dispersive X-ray Spectroscopy (EDS) analysis. The samples were also characterized by higher oxidation and high-temperature corrosion rates in comparison to the samples produced with low energy input. These results prove the applicability of an optical emission spectroscopic system for monitoring DED to identify process conditions leading to compositional changes and variation in the quality of the built material.

  • 86.
    Kisielewicz, Agnieszka
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Production Systems.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Production Systems.
    Ancona, Antonio
    University West, Department of Engineering Science, Division of Production Systems.
    Spectroscopic monitoring of laser blown powder directed energy deposition of Alloy 7182018In: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, p. 418-425Article in journal (Refereed)
    Abstract [en]

    Experimental explorations of a spectrometer system used for in-process monitoring of the laser blown powder directed energy deposition of Alloy 718 is presented. Additive manufacturing of metals using this laser process experiences repeated heating and cooling cycles which will influence the final microstructure and chemical composition at every given point in the built. The spectrometer system disclosed, under certain process conditions, spectral lines that indicate vaporisation of chromium. Post process scanning electron microscope energy dispersive spectroscopy analysis of the deposited beads confirmed a reduction of chromium. Since the chromium concentration in Alloy 718 is correlated to corrosion resistance, this result encourages to further investigations including corrosion tests.

  • 87.
    Kumar, Rajiv
    et al.
    IITB-Monash Research Academy, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
    Joardar, Joydip
    International Advanced Research Centre for Powder Metallurgy and New Materials, Hyderabad, India.
    Raman, R.K. Singh
    Department of Mechanical and Aerospace Engineering, Monash University, VIC 3800 Australia.
    Raja, V.S.
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
    Joshi, Shrikant
    University West, Department of Engineering Science, Research Enviroment Production Technology West. International Advanced Research Centre for Powder Metallurgy and New Materials, Hyderabad, India.
    Parida, S.
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
    Effect of chromium and aluminum addition on anisotropic and microstructural characteristics of ball milled nanocrystalline iron2016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 671, p. 164-169Article in journal (Refereed)
    Abstract [en]

    Prior studies on synthesis of nanocrystalline elements have discussed the effect of ball milling on lattice parameter, crystallite size, and micro-strain. For elemental milled powders, the anisotropic peak broadening does not change with increasing milling time. However, the effect of alloying addition on the anisotropic behavior of ball milled nanocrystalline powders remains an unexplored area. Here we report the effect of chromium and aluminum addition on the anisotropic behavior of iron in nanocrystalline Fe–20Cr–5Al (wt%) alloy powders synthesized by ball milling. The experimental results show that the anisotropic behavior of iron changes towards isotropic with milling. This change was also correlated to the theoretically calculated anisotropic factor from the change in elastic constant of iron due to milling. Addition of alloying elements exhibited a monotonic rise in the lattice parameter with crystallite size, which was attributed to the excess grain boundary interfacial energy and excess free volume at grain boundaries. Transmission electron microscopy image confirmed the crystallite size and nature of dislocation obtained using modified Williamson-Hall method.

  • 88.
    Kumara, Chamara
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Balachandramurthi, Arun Ramanathan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Goel, Sneha
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Hanning, Fabian
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Moverare, Johan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Linköping University, Division of Engineering Materials, Department of Management and Engineering, Linköping, SE-58183, Sweden.
    Toward a better understanding of phase transformations in additive manufacturing of Alloy 7182020In: Materialia, E-ISSN 2589-1529, Vol. 13, article id 100862Article in journal (Refereed)
    Abstract [en]

    This paper presents a discussion on the phase-transformation aspects of additively manufactured Alloy 718 during the additive manufacturing (AM) process and subsequent commonly used post-heat treatments. To this end, fundamental theoretical principles, thermodynamic and kinetics modeling, and existing literature data are employed. Two different AM processes, namely, laser-directed energy deposition and electron-beam powder-bed fusion are considered. The general aspects of phase formation during solidification and solid state in Alloy 718 are first examined, followed by a detailed discussion on phase transformations during the two processes and subsequent standard post heat-treatments. The effect of cooling rates, thermal gradients, and thermal cycling on the phase transformation in Alloy 718 during the AM processes are considered. Special attention is given to illustrate how the segregated composition during the solidification could affect the phase transformations in the Alloy 718. The information provided in this study will contribute to a better understanding of the overall process–structure–property relationship in the AM of Alloy 718 718. © 2020

  • 89. Lindgren, L-E.
    et al.
    Lundbäck, A.
    Fisk, M.
    Pedersen, R.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Industrial application of computational welding mechanics2015Conference paper (Refereed)
  • 90.
    Lorentzon, John
    et al.
    University West, School of Business, Economics and IT, Division of Business Administration. University West, Department of Engineering Science, Division of Production Engineering.
    Järvstråt, Niklas
    University West, Department of Engineering Science, Division of Production Engineering.
    Josefson, B. L.
    Chalmers University of Technology, Department of Applied Mechanics.
    Modelling chip formation of alloy 7182009In: Journal of Materials Processing Technology, Vol. 209, no 10, p. 4645-4653Article in journal (Refereed)
  • 91.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Dizdar, S.
    Höganäs AB, Höganäs, Sweden.
    Cavitation-erosion resistance of HVAF-sprayed Fe-based metal coatings for marine applications2017Conference paper (Other academic)
  • 92.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Sato, Kazuto
    Fujimi Incoporated.
    Houdkova, Sarka
    University of West Bohemia.
    Smazalova, Eva
    University of West Bohemia.
    Lusvarghi, Luca
    University of Modena and Reggio Emilia.
    Sassatelli, Paolo
    University of Modena and Reggio Emilia.
    Bolelli, Giovanni
    Università degli Studi di Modena e Reggio Emilia, Modena, Italy.
    Tribological Properties of Hard Metal Coatings Sprayed by High Velocity Air Fuel Process2015In: Proceedings of the International Thermal Spray Conference, ASM International, 2015, p. 761-766Conference paper (Refereed)
    Abstract [en]

    Lowering the thermal energy and increasing the kinetic energy of sprayed particles by newly developed HVAF systems can significantly reduce material decarburization, and increases sliding wear and corrosion resistance of hard metal coatings, making HVAF coatings attractive both economically and environmentally over its HVOFs predecessors. Two agglomerated and sintered feedstock powder chemistries, respectively WC-Co (88/12) and WC-CoCr (86/10/4), with increasing primary carbides grain size from 0.2 to 4.0 microns, have been deposited by the latest HVAF-M3 process onto carbon steel substrates. Respective dry sliding wear behaviours and friction coefficients were evaluated at room temperature via Ball-on-disk (ASTM G99-90) wear tests against Al2O3 counterparts, and via Pin-on-disk (ASTM G77-05) wear tests against modified martensitic steel counterparts in both dry and lubricated conditions. Sliding wear mechanisms, with formation of wavy surface morphology and brittle cracking, are discussed regarding the distribution and size of primary carbides. Corrosion behaviours were evaluated via standard Neutral Salt Spray (NSS), Acetic Acid Salt Spray (AASS), accelerated corrosion test and electrochemical polarization test at room temperature. Optimization of coating tribological properties are discussed regarding the suitable selection of primary carbide size for different working load applications

  • 93.
    Majid, Farajian
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Järvstråt, Niklas
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Surface geometry measurements and the experimental and numerical investigation of stress concentration in fillet welds2006In: 59th Annual Assembly and the International Conference of the International Institute of Welding: Sep, Quebec, Canada, 2006Conference paper (Other academic)
  • 94.
    Markocsan, Nicolaie
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Turunen, Erja
    Tampere University of Technology.
    Vuoristo, Petri
    Tampere University of Technology.
    Wigren, Jan
    Volvo Aero Corporation, Trollhättan.
    Thermal spraying in Europe’s Nordic region2007In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 16, no 4, p. 463-464Article in journal (Refereed)
  • 95.
    Markocsan, Nicolaie
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Wigren, Jan
    Volvo Aero Corporation, Surface Technology,Trollhättan.
    Li, X.-H
    Siemens Industrial Turbomachinery,Department of GRDM, Finspång.
    Low thermal conductivity coatings for gas turbine applications2007In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 16, no 4, p. 498-505Article in journal (Refereed)
  • 96.
    Mraz, Lubos
    et al.
    Welding Research Institute - Industrial Institute SR, Račianska 71, 83259 Bratislava, Slovakia .
    Karlsson, Leif
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Mikula, Pavol
    Nuclear Physics Institute ASCR v.v.i., 250 68 Řež, Czech Republic .
    Vrana, Miroslav
    Nuclear Physics Institute ASCR v.v.i., 250 68 Řež, Czech Republic .
    Identification of Weld Residual Stresses Using Diffraction Methods and their Effect on Fatigue Strength of High Strength Steels Welds2014In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 768-769, p. 668-674Article in journal (Refereed)
    Abstract [en]

    It is well known that fatigue strength of welded joints does not depend on steel strength. Better fatigue strength of welded joints, e.g. longer life time of fatigue loaded weld structures, can be achieved with a smooth transition between the weld and the base material to minimize stress concentration. It has also been recognized that residual stresses play a critical role in the fatigue behaviour of welds. In the last decade an extensive research has been performed in order to increase the fatigue strength of high strength steel weldments. The martensite and bainite transformation start temperatures of weld metals have been shown to have a large effect on fatigue life time of high strength steel welds. This is of particular importance if the full potential of high strength steels is to be used in fatigue loaded constructions. A detailed investigation of the effect of phase transformation temperature on residual stress distribution in the vicinity high strength steel welds and its effect on fatigue life time has been performed. The transformation temperature of the weld metal was varied by changing the chemical composition of the filler material. Residual stress distributions have been measured by neutron as well as by X-ray diffraction and fatigue tests have been performed on the fillet welds. A strong effect of weld metal phase transformation temperature on residual stress level was observed. Fatigue strength increased approximately three times when an optimised low transformation temperature filler material was used in comparison to the application of conventional filler material

  • 97.
    Mraz, Lubos
    et al.
    Welding Research Institute - Industrial Institute SR, 832 59 Bratislava, Slovakia.
    Karlsson, Leif
    University West, Department of Engineering Science, Divison of Natural Sciences, Surveying and Mechanical Engineering.
    Vrana, Miroslav
    Nuclear Physics Institute ASCR, v.v.i, 25068 Rez, Czech Republic .
    Mikula, Pavol
    Nuclear Physics Institute ASCR, v.v.i, 25068 Rez, Czech Republic .
    Residual stress distributions at high strength steel welds prepared by low transformation temperature (LTT) and conventional welding consumables2014In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 777, p. 40-45Article in journal (Refereed)
    Abstract [en]

    Residual stress distributions in fillet welds in 8 mm 900 MPa steel have been mapped perpendicular and parallel to the weld line and also through the thickness in the vicinity of weld toe position. Measurements were carried out on four welds when two of them were performed with conventional and two with the so called LTT (low transformation temperature) filler materials. Both neutron and X-ray diffractions were used for determination of the residual stress distribution. Fatigue properties have also been evaluated for all test welds. Neutron diffraction measurements showed that the stress profiles perpendicular to the weld toe qualitatively did not depend on filler material type although the absolute stress levels differed. Trends were similar for positions 2, 4 and 6 millimetres below the surface for all three stress components; σx (direction perpendicular to the weld), σy (parallel to the weld) and σz (through the thickness). X-ray diffraction showed difference in residual stress level at the weld toe. Lower residual stress levels have been identified for LTT filler material when compared to the conventional consumable compositions. The effect of residual stress is discussed in relation to fatigue properties of all four welds. Remarkable higher fatigue strength has been measured for welds prepared by the LTT filler materials. © (2014) Trans Tech Publications, Switzerland.

  • 98.
    Mráz, Lubos
    et al.
    Welding Reseach Insitute - Industrial Insitute of SR, Racinska 71, 832 59 Bratislava, Slovak Republic.
    Karlsson, Leif
    University West, Department of Engineering Science, Divison of Natural Sciences, Surveying and Mechanical Engineering.
    Vrána, Miroslav
    Nuclear Physics Institute AS CR, v.v.i., Řež 130, Czech Republic ..
    Neutron Diffraction Studies of Residual Stress Distribution in the Vicinity of the Single Pass Fillet Steel Welds2015In: Applied Mechanics and Materials, ISSN 1660-9336, E-ISSN 1662-7482, Vol. 732, p. 13-19Article in journal (Refereed)
    Abstract [en]

    In this contribution the results of residual strain/stress measurements performed on several single pass fillet steel welds, which were carried out at different welding conditions, namely, with different filler materials are presented.

  • 99.
    Mráz, Lubos
    et al.
    Welding Research Institute, Industrial Institute SR, Bratislava, Slovakia .
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Vrána, Miroslav
    Nuclear Physics Institute AS CR, v.v.i., Řež 130, Czech Republic .
    Mikula, Pavol
    Nuclear Physics Institute AS CR, v.v.i., Řež 130, Czech Republic .
    Residual stress distribution measurement by neutron diffraction of the single pass fillet steel welds2014In: 52nd International Scientific Conference on Experimental Stress Analysis (EAN 2014): Proceedings of a meeting held 2-5 June 2014, Marianske Lazne, Czech Republic., Czech Society for Mechanics ( CSM ) , 2014Conference paper (Refereed)
    Abstract [en]

    In this contribution the results of residual strain/stress measurements performed on several single pass fillet steel welds which were carried out at different welding conditions, namely, with different filler materials are presented.

  • 100.
    Neikter, Magnus
    et al.
    Luleå University of Technology, Div. Material Science, Luleå, Sweden.
    Forsberg, Fredrik
    Luleå University of Technology, Div. Fluid and Experimental Mechanics, Luleå, Sweden.
    Lycksam, Henrik
    Luleå University of Technology, Div. Fluid and Experimental Mechanics, Luleå, Sweden.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology.
    Antti, Marta-Lena
    Luleå University of Technology, Div. Material Science, Luleå, Sweden.
    Microstructure and Defects in Additive Manufactured Titanium: a Comparison Between Microtomography and Optical Microscopy2017Conference paper (Other academic)
    Abstract [en]

    The aim of this work has been to compare two different analysing methods; x-ray microtomography and light optical microscopy, when it comes to defects and microstructure of additively manufactured Ti-6Al-4V. The results show that both techniques have their pros and cons:microtomography is the preferred choice for defect detection by analysing the full 3D sample volume, while light optical microscopy is better for analysing finer details in 2D.

123 51 - 100 of 132
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf