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Jansson, Ulf
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Publications (10 of 226) Show all publications
Tidén, S., Abenayake, H., Löfstrand, J., Jansson, U. & Sahlberg, M. (2024). Crack reduction in laser powder bed fusion of MnAl(C) using graphene oxide coated powders. Scientific Reports, 14, Article ID 1142.
Open this publication in new window or tab >>Crack reduction in laser powder bed fusion of MnAl(C) using graphene oxide coated powders
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2024 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 14, article id 1142Article in journal (Refereed) Published
Abstract [en]

MnAl(C) is a promising candidate as a rare earth free magnet. When processing MnAl(C) in laser powder bed fusion (L-PBF) the high cooling rates can retain the high temperature epsilon-phase which can then be annealed at low temperatures to yield the ferromagnetic tau-phase. However, MnAl(C) has been shown to be difficult to print using L-PBF and the material is prone to severe cracking. In this study, we have investigated how the addition of a graphene oxide (GO) coating on the powders can affect the processability of MnAl(C) and properties of the printed parts. MnAl(C) powders were coated with 0.2 wt.% GO using a wet-chemical process. The addition of GO reduced crack formation in the printed parts, and also influenced the degree of < 001 > texture along the build direction. After printing, densities of 93% and 87% could be achieved for the reference and 0.2 wt.% GO, respectively. Furthermore, a 35% reduction of cracking was calculated from image analysis, comparing printed samples produced from coated and non-coated powders. Both powders formed mostly the e-phase but some two-phase regions with a mix of γ- and ε-phase could be observed in the as-printed parts, but seemed to be more prominent in the uncoated reference samples and could also be linked to cracks. The τ-phase together with smaller amounts of secondary phases was obtained after heat treatment at 560 degrees C for 5 min for both samples. Vibrating sample magnetometry was used to measure the magnetic properties, the reference had a remanence of 33Am2/ kg and a coercivity of 139 kA/m, and the 0.2 wt.% GO sample showed a similar remanence of 30Am2/ kg and coercivity of 130 kA/m. These results show that GO coating is a viable method to reduce detrimental cracking in L-PBF MnAl without reducing the magnetic performance of the material.

Place, publisher, year, edition, pages
Springer Nature, 2024
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-523948 (URN)10.1038/s41598-024-51283-5 (DOI)001142462100014 ()38212350 (PubMedID)
Funder
Swedish Research Council, 2022-03069
Available from: 2024-02-27 Created: 2024-02-27 Last updated: 2024-03-28Bibliographically approved
Fritze, S., Hahn, R., Aboulfadl, H., Johansson, F. O. .., Lindblad, R., Böör, K., . . . Thuvander, M. (2024). Elemental distribution and fracture properties of magnetron sputtered carbon supersaturated tungsten films. Surface & Coatings Technology, 477, Article ID 130326.
Open this publication in new window or tab >>Elemental distribution and fracture properties of magnetron sputtered carbon supersaturated tungsten films
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2024 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 477, article id 130326Article in journal (Refereed) Published
Abstract [en]

The combination of strength and toughness is a major driving force for alloy design of protective coatings, and nanocrystalline tungsten (W)-alloys have shown to be promising candidates for combining strength and toughness. Here we investigate the elemental distribution and the fracture toughness of carbon (C) alloyed W thin films prepared by non-reactive magnetron sputtering. W:C films with up to ~4 at.% C crystallize in a body-centered-cubic structure with a strong 〈hh0〉texture, and no additional carbide phases are observed in the diffraction pattern. Atom probe tomography and X-ray photoelectron spectroscopy confirmed the formation of such a supersaturated solid solution. The pure W film has a hardness ~13 GPa and the W:C films exhibit a peak hardness of ~24 GPa. In-situ micromechanical cantilever bending tests show that the fracture toughness decreases from ~4.5 MPa·m1/2 for the W film to ~3.1 MPa·m1/2 for W:C films. The results show that C can significantly enhance the hardness of W thin films while retaining a high fracture toughness.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
PVD, Fracture toughness, Atom probe tomography, XPS, Tungsten
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-521828 (URN)10.1016/j.surfcoat.2023.130326 (DOI)001149676000001 ()
Funder
Swedish Foundation for Strategic Research, RMA15-0048
Available from: 2024-01-29 Created: 2024-01-29 Last updated: 2024-02-15Bibliographically approved
Osinger, B., Donzel-Gargand, O., Fritze, S., Jansson, U. & Lewin, E. (2024). Structural and mechanical properties of magnetron sputtered (NbxMo1-x)C thin films. Vacuum, 224, Article ID 113146.
Open this publication in new window or tab >>Structural and mechanical properties of magnetron sputtered (NbxMo1-x)C thin films
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2024 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 224, article id 113146Article in journal (Refereed) Published
Abstract [en]

While transition metal carbides (TMCs) exhibit favourable mechanical properties, alloying according to the valence electron concentration (VEC) has the potential to further enhance the properties of these hard but inherently brittle materials. This study investigates the influence of alloying on the microstructure and mechanical properties of (NbxMo1-x)C carbide films, including binary references and ternary compositions with varying metal ratios (x between 0.35 and 0.53). Furthermore, the influence of various substrate materials is studied by comparing films deposited on Al2O3, MgO and SiO2. All films exhibit a NaCl-type carbide structure and X-ray photoelectron spectroscopy revealed the presence of small amounts of an additional amorphous carbon (a-C) phase. Hardness values around 20 ± 2 GPa were obtained for the films on Al2O3 and MgO, whereas a reduced hardness of 11 ± 1 GPa was observed for the films on SiO2 which is attributed to larger crystallite size and more polycrystalline structure. Overall no clear trend as a function of composition can be noted, indicating that microstructure effects dominate the mechanical properties in this study overshadowing the effect of varying the metal content.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Magnetron sputtering, Ceramic coating, Transition metal carbides, Mechanical properties
National Category
Materials Chemistry
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-517298 (URN)10.1016/j.vacuum.2024.113146 (DOI)001218592400001 ()
Funder
Swedish Research Council, 2018-04834Swedish Research Council, 2017-00646_9Swedish Foundation for Strategic Research, RIF14-0053
Available from: 2024-01-09 Created: 2024-01-09 Last updated: 2024-05-31Bibliographically approved
Tidén, S., Taher, M., Vennstrom, M. & Jansson, U. (2023). Additive Manufacturing of Cu Using Graphene-Oxide-Treated Powder. Materials, 16(15), Article ID 5216.
Open this publication in new window or tab >>Additive Manufacturing of Cu Using Graphene-Oxide-Treated Powder
2023 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 16, no 15, article id 5216Article in journal (Refereed) Published
Abstract [en]

Additive manufacturing of Cu is interesting for many applications where high thermal and electric conductivity are required. A problem with printing of Cu with a laser-based process is the high reflectance of the powder for near-infrared wavelengths making it difficult to print components with a high density. In this study, we have investigated laser bed fusion (L-PBF) of Cu using graphene oxide (GO)-coated powder. The powder particles were coated in a simple wet-chemical process using electrostatic attractions between the GO and the powder surface. The coated powder exhibited a reduced reflectivity, which improved the printability and increased the densities from similar to 90% for uncoated powder to 99.8% using 0.1 wt% GO and a laser power of 500W. The coated Cu powders showed a tendency for balling using laser powers below 400 W, and increasing the GO concentration from 0.1 to 0.3 wt.% showed an increase in spattering and reduced density. Graphene-like sheet structures could be observed in the printed parts using scanning electron microscopy (SEM). Carbon-filled inclusions with sizes ranging from 10-200 nm could also be observed in the printed parts using transmission electron microscopy (TEM). The GO treatment yielded parts with higher hardness (75.7 HV) and electrical conductivity (77.8% IACS) compared to the parts printed with reference Cu powder.

Place, publisher, year, edition, pages
MDPI AG, 2023
Keywords
Cu, graphene oxide, GO, SLM, additive manufacturing, AM, laser powder bed fusion, LPBF
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:uu:diva-510002 (URN)10.3390/ma16155216 (DOI)001045566700001 ()37569920 (PubMedID)
Available from: 2023-08-28 Created: 2023-08-28 Last updated: 2024-02-27Bibliographically approved
Goetz, I. K., Pacheco, V., Hassila, C. J., Jansson, U., Schneider, J. M. & Hans, M. (2023). Convective Flow Redistribution of Oxygen by Laser Melting of a Zr-Based Amorphous Alloy. Materials, 16(11), Article ID 4113.
Open this publication in new window or tab >>Convective Flow Redistribution of Oxygen by Laser Melting of a Zr-Based Amorphous Alloy
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2023 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 16, no 11, article id 4113Article in journal (Refereed) Published
Abstract [en]

Oxygen impurities play a crucial role in the glass-forming ability and crystallisation behaviour of metallic glasses. In the present work, single laser tracks were produced on Zr59.3-xCu28.8 Al10.4Nb1.5Ox substrates (x = 0.3, 1.3) to study the redistribution of oxygen in the melt pool under laser melting, which provides the basis for laser powder bed fusion additive manufacturing. Since such substrates are commercially not available, they were fabricated by arc melting and splat quenching. X-ray diffraction revealed that the substrate with 0.3 at.% oxygen was X-ray amorphous, while the substrate with 1.3 at.% oxygen was partially crystalline. Hence, it is evident that the oxygen content affects the crystallisation kinetics. Subsequently, single laser tracks were produced on the surface of these substrates, and the melt pools attained from the laser processing were characterised by atom probe tomography and transmission electron microscopy. Surface oxidation and subsequent convective flow redistribution of oxygen by laser melting were identified as causes of the presence of CuOx and crystalline ZrO nanoparticles in the melt pool. Bands of ZrO likely originate from surface oxides that were moved deeper into the melt pool by convective flow. The findings presented here highlight the influence of oxygen redistribution from the surface into the melt pool during laser processing.

Place, publisher, year, edition, pages
MDPI, 2023
Keywords
bulk metallic glass, single laser tracks, oxygen contamination, surface oxides, atom probe tomography, transmission electron microscopy
National Category
Other Physics Topics
Identifiers
urn:nbn:se:uu:diva-495462 (URN)10.3390/ma16114113 (DOI)001005565800001 ()37297246 (PubMedID)
Funder
Swedish Foundation for Strategic Research, GMT14-0048
Available from: 2023-01-27 Created: 2023-01-27 Last updated: 2023-06-30Bibliographically approved
Zendejas Medina, L., Mølmen, L., Paschalidou, E.-M., Donzel-Gargand, O., Leisner, P., Jansson, U. & Nyholm, L. (2023). Extending the Passive Region of CrFeNi-Based High Entropy Alloys. Advanced Functional Materials, 33(51), Article ID 2307897.
Open this publication in new window or tab >>Extending the Passive Region of CrFeNi-Based High Entropy Alloys
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2023 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 33, no 51, article id 2307897Article in journal (Refereed) Published
Abstract [en]

This study provides principles for designing new corrosion resistant high entropy alloys. The theoretical framework is a percolation model developed by Newman and Sieradzki that predicts the ability of an alloy to passivate, i.e., to form a protective surface oxide, based on its composition. Here, their model is applied to more complex materials than previously, namely amorphous CrFeNiTa and CrFeNiW alloys. Furthermore, the model describes a more complex passivation process: reforming the oxide layer above the transpassive potential of Cr. The model is used to predict the lowest concentration of Ta or W required to extend the passive region, yielding 11–14 at% Ta and 14–17 at% W. For CrFeNiTa, experiments reveal a threshold value of 13–15 at% Ta, which agrees with the prediction. For CrFeNiW, the experimentally determined threshold value is 37–45 at% W, far above the predicted value. Further investigations explore why the percolation model fails to describe the CrFeNiW system; key factors are the higher nobility and the pH sensitivity of W. These results demonstrate some limitations of the percolation model and offer complementary passivation criteria, while providing a design route for combining the properties of the 3d transition metal and refractory metal groups.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2023
Keywords
corrosion, thin film, coating, high entropy alloy, percolation theory
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-489915 (URN)10.1002/adfm.202307897 (DOI)001062551700001 ()
Funder
Vinnova, 2016-05156Swedish Research Council, 2019-00207Swedish Foundation for Strategic Research, ARC19-0026Knowledge Foundation
Note

Title in the list of papers of León Zendejas Medina's thesis: Extending the passive region of CrFeNi-based high entropy alloys by including Ta or W

Available from: 2022-12-06 Created: 2022-12-06 Last updated: 2024-05-21Bibliographically approved
Tunes, M. A., Fritze, S., Osinger, B., Willenshofer, P., Alvarado, A. M., Martinez, E., . . . El-Atwani, O. (2023). From high-entropy alloys to high-entropy ceramics: The radiation-resistant highly concentrated refractory carbide (CrNbTaTiW)C. Acta Materialia, 250, Article ID 118856.
Open this publication in new window or tab >>From high-entropy alloys to high-entropy ceramics: The radiation-resistant highly concentrated refractory carbide (CrNbTaTiW)C
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2023 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 250, article id 118856Article in journal (Refereed) Published
Abstract [en]

High-entropy materials represent the state-of-the-art on the alloy design strategy for future applications in extreme environments. Recent data indicates that high-entropy alloys (HEAs) exhibit outstanding radiation resistance in face of existing diluted alloy counterparts due to suppressed damage formation and evolution. An extension of the HEA concept is presented in this paper towards the synthesis and characterization of novel high-entropy ceramics as emergent materials for application in environments where energetic particle irradiation is a major concern. A novel carbide within the quinary refractory system CrNbTaTiW has been synthesized using magnetron-sputtering. The material exhibited nanocrystalline grains, single-phase crystal structure and C content around 50 at.%. Heavy-ion irradiation with in-situ Transmission Electron Microscopy was used to assess the irradiation response of the new high-entropy carbide (HEC) at 573 K and a comparison with the HEA within the system is made. No displacement damage effects appear within the microstructures of both HEA and HEC up to a dose of 10 displacements-per-atom. Surprisingly, the HEC has not amorphized under the investigated conditions. Xe was implanted in both materials and bubbles nucleated, but smaller sizes compared with conventional nuclear materials shedding light they are potential candidates for use in nuclear energy.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
High-entropy ceramics, High-entropy alloys, Nanocrystalline materials, Radiation damage, Extreme environments
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-499313 (URN)10.1016/j.actamat.2023.118856 (DOI)000958714700001 ()
Funder
EU, European Research Council, 757961Swedish Research Council, 2017-00646_9Swedish Research Council, 2019_00191Swedish Foundation for Strategic Research, RIF14-0053
Available from: 2023-03-27 Created: 2023-03-27 Last updated: 2024-01-11Bibliographically approved
Zendejas Medina, L., de Costa, M. V., Donzel-Gargand, O., Nyholm, L., Gamstedt, E. K. & Jansson, U. (2023). Magnetron sputtered high entropy alloy/amorphous carbon nanocomposite coatings. Materials Today Communications, 37, Article ID 107389.
Open this publication in new window or tab >>Magnetron sputtered high entropy alloy/amorphous carbon nanocomposite coatings
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2023 (English)In: Materials Today Communications, ISSN 2352-4928, Vol. 37, article id 107389Article in journal (Refereed) Published
Abstract [en]

Magnetron sputter deposition of metal/carbon nanocomposites has been explored for many metals and a few alloys. In this paper, the formation of nanocomposites based on complex high entropy alloys (HEAs) was explored, focusing on the effect of the average carbon affinity on the phase formation. Two HEA systems were compared: CoCrFeMnNi and Cr26Fe27Ni27Ta20. For each alloy, around 20-50 at% carbon was added through combinatorial co-sputtering. Thermodynamic calculations predicted decomposition of these materials into multiple alloy phases, metal carbides, and, at higher concentrations, free graphitic carbon. Free carbon was found in the coatings at carbon concentrations above 28 and 33 at% for the CoCrFeMnNi and Cr26Fe27Ni27Ta20 systems, respectively, which agreed with the theoretical predictions. However, the segregation of metallic ele-ments and the formation of crystalline carbides were suppressed by the rapid quenching during deposition. All coatings were, instead, amorphous and consisted of either a single metallic phase or a mixture of a metallic phase and sp2- and sp3-hybridized carbon. Mechanical and electrochemical tests were performed, including in-situ fragmentation tests to quantify the crack resistance. The presence of free carbon made the coatings softer than the corresponding single-phase materials. Under tensile strain, the nanocomposite coatings formed a larger number of narrower cracks and exhibited less delamination at high strains.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Magnetron sputtering, Nanocomposite, Amorphous carbon, Fragmentation test
National Category
Materials Chemistry Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-518095 (URN)10.1016/j.mtcomm.2023.107389 (DOI)001104007800001 ()
Funder
Swedish Research Council, 2019-00207Vinnova, 2016-05156
Available from: 2024-01-03 Created: 2024-01-03 Last updated: 2024-01-03Bibliographically approved
Jansson, A., Zendejas Medina, L., Lautrup, L. & Jansson, U. (2023). Magnetron sputtering of the high entropy alloy CoCrFeMnNi on 316L: Influence of substrate grain orientations. Surface & Coatings Technology, 466, Article ID 129612.
Open this publication in new window or tab >>Magnetron sputtering of the high entropy alloy CoCrFeMnNi on 316L: Influence of substrate grain orientations
2023 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 466, article id 129612Article in journal (Refereed) Published
Abstract [en]

This study explores the influence of a 316L stainless steel substrate on the magnetron sputtering of the Cantor alloy CoCrFeMnNi at different substrate bias. The study was carried out on a polycrystalline 316L substrate where the growth behavior of the coating could be investigated on grains with different orientations. By combining electron backscatter diffraction (EBSD) before and after deposition and characterization of the same area, it was possible to determine growth behaviour and surface morphologies on individual substrate grains. No strong influence of the substrate was observed at a floating bias. At a bias of -100V, however, the coating was strongly influenced by the orientation of the individual substrate grains.  Epitaxial coating grains with a smooth surface were observed on the [102]-oriented grains while a more columnar growth was observed on [111]-oriented grains.  Furthermore, a small difference in growth rate was observed on different substrate orientations. The growth behaviour could be related to differences in surface energies and diffusion rates on different surface orientations.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
thin film, coating, high entropy alloy
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-489912 (URN)10.1016/j.surfcoat.2023.129612 (DOI)001010940500001 ()
Funder
Vinnova, 2016-05156
Available from: 2022-12-06 Created: 2022-12-06 Last updated: 2023-10-05Bibliographically approved
Götz, I. K., Kaplan, M., Hans, M., Ström, P., Jansson, U., Hjörvarsson, B. & Schneider, J. M. (2023). Reactive metal additive manufacturing: Surface near ZrN - metallic glass composite formation and mechanical properties. Additive Manufacturing, 66, Article ID 103457.
Open this publication in new window or tab >>Reactive metal additive manufacturing: Surface near ZrN - metallic glass composite formation and mechanical properties
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2023 (English)In: Additive Manufacturing, ISSN 2214-8604, E-ISSN 2214-7810, Vol. 66, article id 103457Article in journal (Other academic) Published
Abstract [en]

ZrN formation in a Zr-based bulk metallic glass is observed after processing using reactive laser powder bed fusion. Two processing routes employing nitrogen as a reactive process gas are explored: (1) Standard inert processing in argon followed by reactive remelting in nitrogen and (2) reactive processing in nitrogen. Incorporation of nitrogen is depth-dependent and both approaches result in a dispersion of ZrN nanocrystals in the amorphous matrix close to the surface. The process parameters can be adjusted to control the volume fraction of crystalline phases formed. Hence, it is shown that reactive additive manufacturing can be utilised to form bulk metallic glass-ceramic composites in surface near regions. Thereby we demonstrate that the reactive gas atmosphere utilised during additive manufacturing enables local tailoring of structure, composition, and mechanical properties in the vicinity of the surface.

Place, publisher, year, edition, pages
Elsevier, 2023
National Category
Other Physics Topics
Identifiers
urn:nbn:se:uu:diva-495463 (URN)10.1016/j.addma.2023.103457 (DOI)000953738800001 ()
Funder
Swedish Foundation for Strategic Research, GMT14-0048Swedish Foundation for Strategic Research, RIF14-0053Swedish Research Council, 2017-00646_9Swedish Research Council, 2019_00191
Available from: 2023-01-27 Created: 2023-01-27 Last updated: 2023-04-25Bibliographically approved
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