Change search
Refine search result
1 - 15 of 15
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.
  • 1.
    Balachandramurthi, Arun Ramanathan
    et al.
    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, Department of Management and Engineering, Linköping, Sweden.
    Dixit, Nikhil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Deng, Dunyong
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Microstructural influence on fatigue crack propagation during high cycle fatigue testing of additively manufactured Alloy 7182019In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 149, p. 82-94Article in journal (Refereed)
    Abstract [en]

    A study of the microstructure of additively manufactured Alloy 718 was performed in order to better understand the parameters that have an influence on the fatigue properties of the material. The specimens were manufactured using two powder bed fusion techniques – Electron Beam Melting (EBM) and Selective Laser Melting (SLM). Four point bending fatigue tests were performed at room temperature with a stress ratio of R = 0.1 and 20 Hz frequency, on material that was either in hot isostatically pressed (HIP) and solution treated and aged (STA) condition or in STA condition without a prior HIP treatment. The grains in the SLM material in the HIP + STA condition have grown considerably both in the hatch and the contour regions; EBM material, in contrast, shows grain growth only in the contour region. Fractographic analysis of the specimens in HIP + STA condition showed a faceted appearance while the specimens in STA condition showed a more planar crack appearance. The crack propagation occurred in a transgranular mode and it was found that precipitatessuch as NbC, TiN or δ-phase, when present, did not affect the crack path. The areas with larger grains corresponded to the faceted appearance of the fracture surface. This could be attributed to the plastic zone ahead of the crack tip being confined within one grain, in case of the larger grains, which promotes single shear crack growth mode

  • 2.
    Balachandramurthi, Arun Ramanathan
    et al.
    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, Department of Management and Engineering, Linköping, Sweden.
    Dixit, Nikhil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology.
    Influence of defects and as-built surface roughness on fatigue properties of additively manufactured Alloy 7182018In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 735, p. 463-474Article in journal (Refereed)
    Abstract [en]

    Electron beam melting (EBM) and Selective Laser Melting (SLM) are powder bed based additive manufacturing (AM) processes. These, relatively new, processes offer advantages such as near net shaping, manufacturing complex geometries with a design space that was previously not accessible with conventional manufacturing processes, part consolidation to reduce number of assemblies, shorter time to market etc. The aerospace and gas turbine industries have shown interest in the EBM and the SLM processes to enable topology-optimized designs, parts with lattice structures and part consolidation. However, to realize such advantages, factors affecting the mechanical properties must be well understood – especially the fatigue properties. In the context of fatigue performance, apart from the effect of different phases in the material, the effect of defects in terms of both the amount and distribution and the effect of “rough” as-built surface must be studied in detail. Fatigue properties of Alloy 718, a Ni-Fe based superalloy widely used in the aerospace engines is investigated in this study. Four point bending fatigue tests have been performed at 20 Hz in room temperature at different stress ranges to compare the performance of the EBM and the SLM material to the wrought material. The experiment aims to assess the differences in fatigue properties between the two powder bed AM processes as well as assess the effect of two post-treatment methods namely – machining and hot isostatic pressing (HIP). Fractography and metallography have been performed to explain the observed properties. Both HIPing and machining improve the fatigue performance; however, a large scatter is observed for machined specimens. Fatigue properties of SLM material approach that of wrought material while in EBM material defects severely affect the fatigue life. © 2018 Elsevier B.V.

  • 3.
    Balachandramurthi, Arun Ramanathan
    et al.
    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.
    Snis, Anders
    Arcam EBM, SE-431 37, M€olndal, Sweden.
    Moverare, Johan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Department of Management and Engineering, Link€oping University, SE-581 83, Sweden.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Microstructure tailoring in Electron Beam Powder Bed Fusion Additive Manufacturing and its potential consequences2019In: Results in Materials, ISSN 2590-048X, Vol. 1Article in journal (Refereed)
    Abstract [en]

    Electron Beam Powder Bed Fusion process for Alloy 718 was investigated, in the sense of microstructural evolution with varying process conditions. The existence of a geometric relationship between the melt front and the processing parameters was observed. By understanding and capitalizing on this relationship, it was possible to obtain columnar, equiaxed or bimodal microstructure.

  • 4.
    Balachandramurthi Ramanathan, Arun
    et al.
    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, Department of Management and Engineering, SE 581 83 Linköping, Sweden.
    Mahade, Satyapal
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Additive Manufacturing of Alloy 718 via Electron Beam Melting: Effect of Post-Treatment on the Microstructure and the Mechanical Properties.2018In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 1, article id E68Article in journal (Refereed)
    Abstract [en]

    Alloy 718 finds application in gas turbine engine components, such as turbine disks, compressor blades and so forth, due to its excellent mechanical and corrosion properties at elevated temperatures. Electron beam melting (EBM) is a recent addition to the list of additive manufacturing processes and has shown the capability to produce components with unique microstructural features. In this work, Alloy 718 specimens were manufactured using the EBM process with a single batch of virgin plasma atomized powder. One set of as-built specimens was subjected to solution treatment and ageing (STA); another set of as-built specimens was subjected to hot isostatic pressing (HIP), followed by STA (and referred to as HIP+STA). Microstructural analysis of as-built specimens, STA specimens and HIP+STA specimens was carried out using optical microscopy and scanning electron microscopy. Typical columnar microstructure, which is a characteristic of the EBM manufactured alloy, was observed. Hardness evaluation of the as-built, STA and HIP+STA specimens showed that the post-treatments led to an increase in hardness in the range of ~50 HV1. Tensile properties of the three material conditions (as-built, STA and HIP+STA) were evaluated. Post-treatments lead to an increase in the yield strength (YS) and the ultimate tensile strength (UTS). HIP+STA led to improved elongation compared to STA due to the closure of defects but YS and UTS were comparable for the two post-treatment conditions. Fractographic analysis of the tensile tested specimens showed that the closure of shrinkage porosity and the partial healing of lack of fusion (LoF) defects were responsible for improved properties. Fatigue properties were evaluated in both STA and HIP+STA conditions. In addition, three surface conditions were also investigated, namely the 'raw' as-built surface, the machined surface with the contour region and the machined surface without the contour region. Machining off the contour region completely together with HIP+STA led to significant improvement in fatigue performance.

  • 5. Davies, P.
    et al.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Institute of Structural Materials, College of Engineering, Swansea University, Bay Campus, Fabian Way, Swansea SA1 8EN, United Kingdom.
    Coleman, M.
    Institute of Structural Materials, College of Engineering, Swansea University, Bay Campus, Fabian Way, Swansea SA1 8EN, United Kingdom.
    Birosca, S.
    Institute of Structural Materials, College of Engineering, Swansea University, Bay Campus, Fabian Way, Swansea SA1 8EN, United Kingdom.
    The hierarchy of microstructure parameters affecting the tensile ductility in centrifugally cast and forged Ti-834 alloy during high temperature exposure in air2016In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 117, p. 51-67Article in journal (Refereed)
    Abstract [en]

    Ductility regression is the main concern in using Ti-834 titanium alloy at temperatures above 500 °C for aerospace applications. The reduction of ductility in titanium alloys at high temperatures is strongly correlated to the exposure time. In the current study the effect of prolonged exposure at 500 °C on the tensile ductility of two differently processed Ti-834 alloys was investigated. In order to simulate actual Ti-834 processing routes, forged and centrifugally cast materials were used. The tensile tests were conducted on various specimens exposed at 500 °C for 100, 200 and 500 h to observe microstructure feature changes. Moreover, the effect of microstructure, microtexture, α-case, α2 and silicide precipitate coarsening during high temperature exposure was studied thoroughly. The cast alloy was found to have a minimum ductility and failed at 1.8% strain after exposure at 500 °C/500 h when the α-case layer was retained during testing, whilst, the ductility of the forged alloy was unaffected. The effects of individual microstructural parameters on the ductility regression in Ti-834 alloy were quantified. The results showed that 7.1% strain differences between the cast and forged alloy are related to microstructural variations including; morphology, lath widths, grain size and shape, grain orientations and microtexture. A total of 9.6% strain loss was observed in centrifugally cast Ti-834 after aging at 500°C/500 h and quantified as follow; 3.6% due to α-case formation during high temperature exposure, 0.2% due to α2-precipitates coarsening, 4.4% due to further silicide formation and coarsening, 1.4% due to additional microstructure changes during high temperature exposure. Furthermore, silicide coarsening on α/β phase boundaries caused large void formation around the precipitates. A theoretical model supported by experimental observations for silicide precipitation in fully colony and duplex microstructures was established. The element partitioning during exposure caused Al and Ti depletion in the vicinity of the β phase in the lamellae, i.e., αs area. This resulted in lowering the strength of the alloy and facilitated the formation of Ti3(SiZr)2 precipitates. The Al depletion and nano-scale partitioning observed at the αs/β boundaries resulted in easy crack initiation and promoted propagation in the centrifugally cast colony microstructure and reduced the basal slip τcrss. Furthermore, silicides were not formed in αp (high Al, Ti and low Zr areas) in the forged duplex microstructure that promoted superior mechanical performance and ductility over the cast alloy.

    Graphical abstract

  • 6.
    Fargas, G.
    et al.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Barcelona, 08019, Spain. Centre for Research in Multiscale Engineering of Barcelona, Universitat Politècnica de Catalunya, Campus Diagonal Besòs-EEBE, Barcelona, 08019, Spain.
    Roa, J. J.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Barcelona, 08019, Spain. Centre for Research in Multiscale Engineering of Barcelona, Universitat Politècnica de Catalunya, Campus Diagonal Besòs-EEBE, Barcelona, 08019, Spain.
    Sefer, B.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Barcelona, 08019, Spain. Centre for Research in Multiscale Engineering of Barcelona, Universitat Politècnica de Catalunya, Campus Diagonal Besòs-EEBE, Barcelona, 08019, Spain. University of Erlangen-Nuremberg, Institute for Surface Science and Corrosion, Department of Materials Science and Engineering, Erlangen, D-91058, Germany.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology.
    Antti, M. -L
    Division of Materials Science, Luleå University of Technology, Luleå, S-97187, Sweden.
    Mateo, A.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Barcelona, 08019, Spain. Centre for Research in Multiscale Engineering of Barcelona, Universitat Politècnica de Catalunya, Campus Diagonal Besòs-EEBE, Barcelona, 08019, Spain.
    Influence of cyclic thermal treatments on the oxidation behavior of Ti-6Al-2Sn-4Zr-2Mo alloy2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 145, p. 218-224Article in journal (Refereed)
    Abstract [en]

    Ti-6Al-2Sn-4Zr-2Mo is one of the most common titanium alloys for aerospace industry. This alloy experiences oxidation phenomenon at elevated temperatures. In the present study, cyclic thermal treatments were performed in air at 500, 593 and 700 °C, up to 500 cycles, in order to determine the oxidation kinetics and to analyze the oxide scale and alpha-case formation. Moreover, results were compared to those achieved under isothermal conditions to elucidate differences between both thermal conditions. In this sense, metallographic techniques and X-ray diffraction, together with a detailed advanced characterization of the microstructure by Field Emission Scanning Electron Microscopy and Focus Ions Beam, were used to analyze surface oxidation evolution. Results pointed out that cyclic treatments induced a strong increase of the weight gain compared to isothermal treatments. The analysis of the oxide scale revealed the formation of not only rutile, as isothermal treatments, but also anatase. Thickness of the oxide scale was higher for cyclic conditions, while alpha case did not exceed values reached by isothermal treatments and even became lower at 500 °C.

  • 7.
    Fargas, G.
    et al.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Universitat Politècnica de Catalunya, Barcelona, Spain.
    Roa, J.J.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metallúrgica, Barcelona, Spain.
    Sefer, B.
    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, M.-L.
    Luleå University of Technology, Division of Materials Science, S-97187 Luleå, Sweden.
    Mateo, A.
    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.

  • 8.
    Maimaitiyili, Tuerdi
    et al.
    Photons for Engineering and Manufacturing Group, Paul Scherrer Institute, 5232 Villigen, Switzerland ; Malmö universitet, Department of Materials Science and Applied Mathematics, 20506 Malmö, Sweden.
    Woracek, Robin
    European Spallation Source ERIC, 22100 Lund, Sweden ; Nuclear Physics Institute of the CAS, 250 68 Husinec—Rež, Czech Republic.
    Neikter, Magnus
    Luleå University of Technology, Division of Materials Science, 971 81 Luleå, Swed.
    Boin, Mirko
    Department of Microstructure and Residual Stress Analysis, Helmholtz-Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany.
    Wimpory, Robert C.
    Department of Microstructure and Residual Stress Analysis, Helmholtz-Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Strobl, Markus
    European Spallation Source ERIC, 22100 Lund, Sweden ; Nuclear Physics Institute of the CAS, 250 68 Husinec—Rež, Czech Republic ;Neutron Imaging and Applied Materials Group, Paul Scherrer Institute, 5232 Villigen, Switzerland .
    Drakopoulos, Michael
    maging and Microscopy Group, Diamond Light Source Ltd., Oxfordshire OX11 0DE, U.
    Schäfer, Norbert
    Department of Nanoscale Structures and Microscopic Analysis, Helmholtz-Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany.
    Bjerkén, Christina
    Malmö universitet, Department of Materials Science and Applied Mathematics, 20506 Malmö, Sweden.
    Residual Lattice Strain and Phase Distribution in Ti-6Al-4V Produced by Electron Beam Melting2019In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 4, article id 667Article in journal (Refereed)
    Abstract [en]

    Residual stress/strain and microstructure used in additively manufactured material are strongly dependent on process parameter combination. With the aim to better understand and correlate process parameters used in electron beam melting (EBM) of Ti-6Al-4V with resulting phase distributions and residual stress/strains, extensive experimental work has been performed. A large number of polycrystalline Ti-6Al-4V specimens were produced with different optimized EBM process parameter combinations. These specimens were post-sequentially studied by using high-energy X-ray and neutron diffraction. In addition, visible light microscopy, scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) studies were performed and linked to the other findings. Results show that the influence of scan speed and offset focus on resulting residual strain in a fully dense sample was not significant. In contrast to some previous literature, a uniform α- and β-Ti phase distribution was found in all investigated specimens. Furthermore, no strong strain variations along the build direction with respect to the deposition were found. The magnitude of strain in α and β phase show some variations both in the build plane and along the build direction, which seemed to correlate with the size of the primary β grains. However, no relation was found between measured residual strains in α and β phase. Large primary β grains and texture appear to have a strong effect on X-ray based stress results with relatively small beam size, therefore it is suggested to use a large beam for representative bulk measurements and also to consider the prior β grain size in experimental planning, as well as for mathematical modelling.

  • 9.
    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.

  • 10.
    Neikter, Magnus
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Woracek, R.
    European Spallation Source ERIC, Lund, Sweden. Nuclear Physics Institute of the CAZ, Czech Republic.
    Maimaitiyili, T.
    Paul Scherrer Institute, Villigen, Switzerland; Malmö University, Malmö, Sweden.
    Scheffzük, C.
    Karlsruhe Institute of Technology, Karlsruhe, Germany; Frank Laboratory of Neutron Physics, Dubna, Russian Federation.
    Strobl, M.
    Paul Scherrer Institute, Villigen, Switzerland; Niels Bohr Institute, Copenhagen, Denmark; Nuclear Physics Institute of the CAZ, Czech Republic.
    Antti, Marta-Lena
    Luleå University of Technology, Luleå, Sweden.
    Åkerfeldt, P.
    Luleå University of Technology, Luleå, Sweden.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Bjerkén, C.
    Malmö University, Malmö, Sweden.
    Alpha texture variations in additive manufactured Ti-6Al-4V investigated with neutron diffraction2018In: Additive Manufacturing, ISSN 2214-8604, Vol. 23, p. 225-234Article in journal (Refereed)
    Abstract [en]

    Variation of texture in Ti-6Al-4V samples produced by three different additive manufacturing (AM) processes has been studied by neutron time-of-flight (TOF) diffraction. The investigated AM processes were electron beam melting (EBM), selective laser melting (SLM) and laser metal wire deposition (LMwD). Additionally, for the LMwD material separate measurements were done on samples from the top and bottom pieces in order to detect potential texture variations between areas close to and distant from the supporting substrate in the manufacturing process. Electron backscattered diffraction (EBSD) was also performed on material parallel and perpendicular to the build direction to characterize the microstructure. Understanding the context of texture for AM processes is of significant relevance as texture can be linked to anisotropic mechanical behavior. It was found that LMwD had the strongest texture while the two powder bed fusion (PBF) processes EBM and SLM displayed comparatively weaker texture. The texture of EBM and SLM was of the same order of magnitude. These results correlate well with previous microstructural studies. Additionally, texture variations were found in the LMwD sample, where the part closest to the substrate featured stronger texture than the corresponding top part. The crystal direction of the α phase with the strongest texture component was [112¯3]. © 2018 Elsevier B.V.

  • 11.
    Neikter, Magnus
    et al.
    Luleå University of Technology, Division of Materials Science, Luleå 971 81, Sweden.
    Åkerfeldt, P.
    Luleå University of Technology, Division of Materials Science, Luleå 971 81, Sweden.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology.
    Antti, M. -L
    Luleå University of Technology, Division of Materials Science, Luleå 971 81, Sweden.
    Microstructural characterization and comparison of Ti-6Al-4V manufactured with different additive manufacturing processes2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 143, p. 68-75Article in journal (Refereed)
    Abstract [en]

    In this work, the microstructures of Ti-6Al-4V manufactured by different additive manufacturing (AM) processes have been characterized and compared. The microstructural features that were characterized are the α lath thickness, grain boundary α (GB-α) thickness, prior β grain size and α colony size. In addition, the microhardnesses were also measured and compared. The microstructure of shaped metal deposited (SMD) Ti-6Al-4V material showed the smallest variations in α lath size, whereas the material manufactured with laser metal wire deposition-0 (LMwD-0) showed the largest variation. The prior β grain size was found to be smaller in material manufactured with powder bed fusion (PBF) as compared with corresponding material manufactured with the directed energy deposition (DED) processes. Parallel bands were only observed in materials manufactured with DED processes while being non-present in material manufactured with PBF processes.

  • 12.
    Neikter, Magnus
    et al.
    Luleå University of Technology, Division of Materials Science, Luleå.
    Åkerfeldt, P.
    Luleå University of Technology, Division of Materials Science, Luleå.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology.
    Antti, M-L
    Luleå University of Technology, Division of Materials Science, Luleå.
    Microstructure characterisation of Ti-6Al-4V from different additive manufacturing processes2017In: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 258, p. 1-8, article id 012007Article in journal (Refereed)
    Abstract [en]

    The focus of this work has been microstructure characterisation of Ti-6Al-4V manufactured by five different additive manufacturing (AM) processes. The microstructure features being characterised are the prior β size, grain boundary α and α lath thickness. It was found that material manufactured with powder bed fusion processes has smaller prior β grains than the material from directed energy deposition processes. The AM processes with fast cooling rate render in thinner α laths and also thinner, and in some cases discontinuous, grain boundary α. Furthermore, it has been observed that material manufactured with the directed energy deposition processes has parallel bands, except for one condition when the parameters were changed, while the powder bed fusion processes do not have any parallel bands.

  • 13.
    Sefer, Birhan
    et al.
    Division of Materials Science, Luleå University of Technology, Luleå, Sweden / Department of Materials Science and Metallurgical Engineering, Universitat Politècnica de Catalunya, Barcelona, Spain.
    Dobryden, Illia
    Division of Materials Science, Luleå University of Technology, Luleå, Sweden / Division of Surface and Corrosion Science, KTH Royal Institute of Technology, Stockholm, Sweden.
    Almqvist, Nils
    Division of Materials Science, Luleå University of Technology, Luleå, Sweden.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology. Division of Materials Science, Luleå University of Technology, Luleå, Sweden / Research and Technology Centre, GKN Aerospace Engine Systems, Trollhättan, Sweden.
    Antti, Marta-Lena
    Division of Materials Science, Luleå University of Technology, Luleå, Sweden.
    Chemical Milling of Cast Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo Alloys in Hydrofluoric-Nitric Acid Solutions2017In: Corrosion, ISSN 0010-9312, E-ISSN 1938-159X, Vol. 73, no 4, p. 394-407Article in journal (Refereed)
    Abstract [en]

    The behavior of cast Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo during chemical milling in hydrofluoric-nitric (HF-HNO3) acid solutions with 1:3 and 1:11 molar ratios was investigated using electrochemical and atomic force microscopy (AFM) techniques. Faster corrosion rate in 1:3 solutions was measured for Ti-6Al-4V than for Ti-6Al-2Sn-4Zr-2Mo, whereas in 1:11 solution Ti-6Al-2Sn-4Zr-2Mo exhibited higher corrosion rate. Scanning Kelvin probe force microscopy measurements revealed difference in the Volta potential between the α-laths and the β-layers in the Widmansttäten microstructure indicating operation of microgalvanic cells between the microconstituents when in contact with HF-HNO3 solution. The AFM topography measurements demonstrated faster corrosion of the α-laths compared to the β-layers, in both alloys. In 1:3 solutions, higher α/β height difference was measured in Ti-6Al-4V, whereas in 1:11 solution, the difference was higher in Ti-6Al-2Sn-4Zr-2Mo. The results revealed that the chemical milling behavior of the two investigated alloys is controlled by the microscopic corrosion behavior of the individual microconstituents.

  • 14.
    Tolvanen, Sakari
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology. Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Microstructure and Porosity of Laser Welds in Cast Ti-6Al-4V with Addition of Boron2018In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 49A, no 5, p. 1683-1691Article in journal (Refereed)
    Abstract [en]

    Addition of small amounts of boron to cast Ti-6Al-4V alloy has shown to render a finer microstructure and improved mechanical properties. For such an improved alloy to be widely applicable for large aerospace structural components, successful welding of such castings is essential. In the present work, the microstructure and porosity of laser welds in a standard grade cast Ti-6Al-4V alloy as well as two modified alloy versions with different boron concentrations have been investigated. Prior-β grain reconstruction revealed the prior-β grain structure in the weld zones. In fusion zones of the welds, boron was found to refine the grain size significantly and rendered narrow elongated grains. TiB particles in the prior-β grain boundaries in the cast base material restricted grain growth in the heat-affected zone. The TiB particles that existed in the as cast alloys decreased in size in the fusion zones of welds. The hardness in the weld zones was higher than in the base material and boron did not have a significant effect on hardness of the weld zones. The fusion zones were smaller in the boron-modified alloys as compared with Ti-6Al-4V without boron. Computed tomography X-ray investigations of the laser welds showed that pores in the FZ of the boron modified alloys were confined to the lower part of the welds, suggesting that boron addition influences melt pool flow. © 2018 The Author(s)

  • 15.
    Åkerfeldt, Pia
    et al.
    Luleå University of Technology,Division of Materials Science, Luleå, Sweden.
    Hörnqvist Colliander, Magnus
    Chalmers University of Technology, Department of Physics, Göteborg, Sweden.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology. Luleå University of Technology,Division of Materials Science, Luleå, Sweden.
    Antti, Marta-Lena
    Luleå University of Technology,Division of Materials Science, Luleå, Sweden.
    Electron backscatter diffraction characterization of fatigue crack growth in laser metal wire deposited Ti-6Al-4V2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 135, p. 245-256Article in journal (Refereed)
    Abstract [en]

    By additive manufacturing (AM) there is a feasibility of producing near net shape components in basically one step from 3D CAD model to final product. The interest for AM is high and during the past decade a lot of research has been carried out in order to understand the influence from process parameters on the microstructure and furthermore on the mechanical properties. In the present study laser metal wire deposition of Ti-6Al-4V has been studied in detail with regard to its fatigue crack propagation characteristics. Two specimen orientations, parallel and perpendicular to the deposition direction, have been evaluated at room temperature and at 250 °C. No difference in the fatigue crack growth rate could be confirmed for the two specimen orientations. However, in the fractographic study it was observed that the tortuosity varied between certain regions on the fracture surface. The local crack path characteristic could be related to the alpha colony size and/or the crystallographic orientation. Moreover, large areas exhibiting similar crystallographic orientation were observed along the prior beta grain boundaries, which were attributed to the wide alpha colonies frequently observed along the prior beta grain boundaries. © 2017 Elsevier Inc.

1 - 15 of 15
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