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Jansson, Ulf
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Publications (10 of 195) Show all publications
Moro, M. V., Holeňák, R., Medina, L. Z., Jansson, U. & Primetzhofer, D. (2019). Accurate high-resolution depth profiling of magnetron sputtered transition metal alloy films containing light species: A multi-method approach. Thin Solid Films, 686, Article ID 137416.
Open this publication in new window or tab >>Accurate high-resolution depth profiling of magnetron sputtered transition metal alloy films containing light species: A multi-method approach
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2019 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 686, article id 137416Article in journal (Refereed) Published
Abstract [en]

We present an assessment of a multi-method approach based on ion beam analysis to obtain high-resolution depth profiles of the total chemical composition of complex alloy systems. As a model system we employ an alloy based on several transition metals and containing light species. Samples have been investigated by a number of different ion-beam based techniques, i.e., Rutherford Backscattering Spectrometry, Particle-Induced X-ray Emission, Elastic Backscattering Spectrometry and Time-of-Flight/Energy Elastic Recoil Detection Analysis. Sets of spectra obtained from these different techniques were analyzed both independently and following an iterative and self-consistent approach yielding a more accurate depth profile of the sample, including both metallic heavy constituents (Cr, Fe and Ni) as well as the rather reactive light species (C, O) in the alloy. A quantitative comparison in terms of achievable precision and accuracy is made and the limitations of the single method approach are discussed for the different techniques. The multi-method approach is shown to yield significantly improved and accurate information on stoichiometry, depth distribution and thickness of the alloy with the improvements being decisive for a detailed correlation of composition to the material properties such as corrosion strength. The study also shows the increased relative importance of experimental statistics for the achievable accuracy in the multi-method approach.

Keywords
High-resolution, Composition depth profiling, Ion beam analysis, Metal alloys, Magnetron sputtered thin-films
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-390959 (URN)10.1016/j.tsf.2019.137416 (DOI)000480474400001 ()
Funder
Swedish Research Council, 821-2012-5144Swedish Research Council, 2017-00646_9Swedish Research Council, 2018-04834Swedish Foundation for Strategic Research , RIF14-0053Vinnova, 2016-05156Carl Tryggers foundation
Available from: 2019-08-16 Created: 2019-08-16 Last updated: 2019-09-30Bibliographically approved
Karlsson, D., Lindwall, G., Lundback, A., Amnebrink, M., Bostrom, M., Riekehr, L., . . . Jansson, U. (2019). Binder jetting of the AlCoCrFeNi alloy. ADDITIVE MANUFACTURING, 27, 72-79
Open this publication in new window or tab >>Binder jetting of the AlCoCrFeNi alloy
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2019 (English)In: ADDITIVE MANUFACTURING, ISSN 2214-8604, Vol. 27, p. 72-79Article in journal (Refereed) Published
Abstract [en]

High density components of an AlCoCrFeNi alloy, often described as a high-entropy alloy, were manufactured by binder jetting followed by sintering. Thermodynamic calculations using the CALPHAD approach show that the high-entropy alloy is only stable as a single phase in a narrow temperature range below the melting point. At all other temperatures, the alloy will form a mixture of phases, including a sigma phase, which can strongly influence the mechanical properties. The phase stabilities in built AlCoCrFeNi components were investigated by comparing the as-sintered samples with the post-sintering annealed samples at temperatures between 900 degrees C and 1300 degrees C. The as-sintered material shows a dominant B2/bcc structure with additional fcc phase in the grain boundaries and sigma phase precipitating in the grain interior. Annealing experiments between 1000 degrees C and 1100 degrees C inhibit the sigma phase and only a B2/bcc phase with a fcc phase is observed. Increasing the temperature further suppresses the fcc phase in favor for the B2/bcc phases. The mechanical properties are, as expected, dependent on the annealing temperature, with the higher annealing temperature giving an increase in yield strength from 1203 MPa to 1461 MPa and fracture strength from 1996 MPa to 2272 MPa. This can be explained by a hierarchical microstructure with nano-sized precipitates at higher annealing temperatures. The results enlighten the importance of microstructure control, which can be utilized in order to tune the mechanical properties of these alloys. Furthermore, an excellent oxidation resistance was observed with oxide layers with a thickness of less than 5 mu m after 20 h annealing at 1200 degrees C, which would be of great importance for industrial applications.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2019
Keywords
Additive manufacturing, Binder jetting, High-entropy alloy, HEA
National Category
Metallurgy and Metallic Materials Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:uu:diva-387965 (URN)10.1016/j.addma.2019.02.010 (DOI)000466995800008 ()
Funder
Swedish Foundation for Strategic Research , GMT14-0048
Available from: 2019-06-27 Created: 2019-06-27 Last updated: 2019-06-27Bibliographically approved
Jansson, U. & Lewin, E. (2019). Carbon-containing multi-component thin films. Thin Solid Films, 688, Article ID 137411.
Open this publication in new window or tab >>Carbon-containing multi-component thin films
2019 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 688, article id 137411Article, review/survey (Refereed) Published
Abstract [en]

High entropy alloys (HEAs) have been a hot research area for many years. They are solid solutions of at least five elements in approximately equimolar compositions. The HEAs are assumed to be stabilized by a high entropy of mixing favouring a solid solution phase instead of a mixture of intermetallic phases. The importance of entropy of mixing and the true nature of HEAs are debated but the concept has contributed to an interesting development of new alloys. They idea of stabilizing solid solutions with many elements have recently been expanded to nitrides, borides, oxides and carbides. Furthermore, a growing number of thin film studies of these compounds are now published. In this paper we summarise recent results from studies of carbon-containing multi-component thin films based on the HEA concept. We will summarise some general observations connected to "high-entropy" materials. We also describe some general trends in metal-carbon interactions for transition metals and discuss how they should influence the formation of multi-component carbides. A summary of results on bulk multi-component carbide materials is also presented. We review published studies of carbon-containing multi-component thin films mainly deposited with magnetron-sputtering. The crystal structure, microstructure and properties of these films are described. Finally, we highlight some interesting topics for future research.

Keywords
Review, High entropy materials, Multi-component materials, Carbides, Thin-films
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-395626 (URN)10.1016/j.tsf.2019.137411 (DOI)000485256500007 ()
Funder
Swedish Research Council
Available from: 2019-10-23 Created: 2019-10-23 Last updated: 2019-10-23Bibliographically approved
Shinde, D., Fritze, S., Thuvander, M., Malinovskis, P., Riekehr, L., Jansson, U. & Stiller, K. (2019). Elemental Distribution in CrNbTaTiW-C High Entropy Alloy Thin Films. Paper presented at Atom Probe Tomography and Microscopy (APT and M) Conference, JUN 10-15, 2018, Gaithersburg, MD. Microscopy and Microanalysis, 25(2), 489-500
Open this publication in new window or tab >>Elemental Distribution in CrNbTaTiW-C High Entropy Alloy Thin Films
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2019 (English)In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 25, no 2, p. 489-500Article in journal (Refereed) Published
Abstract [en]

The microstructure and distribution of the elements have been studied in thin films of a near-equimolar CrNbTaTiW high entropy alloy (HEA) and films with 8 at.% carbon added to the alloy. The films were deposited by magnetron sputtering at 300 degrees C. X-ray diffraction shows that the near-equimolar metallic film crystallizes in a single-phase body centered cubic (bcc) structure with a strong (110) texture. However, more detailed analyses with transmission electron microscopy (TEM) and atom probe tomography (APT) show a strong segregation of Ti to the grain boundaries forming a very thin Ti-Cr rich interfacial layer. The effect can be explained by the large negative formation enthalpy of Ti-Cr compounds and shows that CrNbTaTiW is not a true HEA at lower temperatures. The addition of 8 at.% carbon leads to the formation of an amorphous structure, which can be explained by the limited solubility of carbon in bcc alloys. TEM energy-dispersive X-ray spectroscopy indicated that all metallic elements are randomly distributed in the film. The APT investigation, however, revealed that carbide-like clusters are present in the amorphous film.

Place, publisher, year, edition, pages
CAMBRIDGE UNIV PRESS, 2019
Keywords
atom probe tomography, carbon clustering, high entropy alloy, segregation, thin film
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-385570 (URN)10.1017/S1431927618016264 (DOI)000466756600025 ()30712522 (PubMedID)
Conference
Atom Probe Tomography and Microscopy (APT and M) Conference, JUN 10-15, 2018, Gaithersburg, MD
Funder
Swedish Research Council, 621-2012-4359Swedish Research Council, 622-2008-405Knut and Alice Wallenberg FoundationSwedish Foundation for Strategic Research , RMA11-0029
Available from: 2019-06-19 Created: 2019-06-19 Last updated: 2019-06-19Bibliographically approved
Karlsson, D., Marshal, A., Johansson, F., Schuisky, M., Sahlberg, M., Schneider, J. M. & Jansson, U. (2019). Elemental segregation in an AlCoCrFeNi high-entropy alloy: A comparison between selective laser melting and induction melting. Journal of Alloys and Compounds, 784, 195-203
Open this publication in new window or tab >>Elemental segregation in an AlCoCrFeNi high-entropy alloy: A comparison between selective laser melting and induction melting
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2019 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 784, p. 195-203Article in journal (Refereed) Published
Abstract [en]

Additive manufacturing of a high-entropy alloy, AlCoCrFeNi, was studied with selective laser melting from gas atomized powder. A wide process parameter window in the SLM process was investigated but it was impossible to produce crack-free samples, attributed to stresses that originate during the building processes. The microstructure and elemental segregation in the SLM samples were compared with induction-melted AlCoCrFeNi. The induction-melted sample crystallizes in randomly oriented large grains (several hundred microns). Dendritic and inter-dendritic areas with slightly different chemical composition can be observed. Within these areas a spinodal decomposition occurs with a separation into FeCr- and NiAl-rich domains. Further spinodal decomposition within the FeCr-rich regions into Cr- and Fe-rich domains was observed by atom probe tomography.

In contrast, the SLM-samples crystallizes in much smaller grains (less than 20 μm) with a dendrite-like substructure. These dendrite-like features exhibit distinct chemical fluctuations on the nm-scale. During annealing more pronounced chemical fluctuations and the formation of Cr-rich and Cr-poor regions can be observed. The difference in microstructure and spinodal decomposition between the induction-melted and SLM samples is attributed to the significantly higher cooling rate for SLM. This study shows that, by using different synthesis pathways, it is possible to modify the microstructure and segregation of element within alloys. This can be used to tune the materials properties, if the cracking behavior is handled e.g. by change of alloy composition to minimize phase transformations or use of a heating stage.

Keywords
Additive manufacturing, Selective laser melting (SLM), High-entropy alloy, Spinodal decomposition
National Category
Metallurgy and Metallic Materials Materials Chemistry Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:uu:diva-379323 (URN)10.1016/j.jallcom.2018.12.267 (DOI)000459796400023 ()
Funder
Swedish Foundation for Strategic Research
Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2019-03-28Bibliographically approved
Fritze, S., Koller, C. M., von Fieandt, L., Malinovskis, P., Johansson, K., Lewin, E., . . . Jansson, U. (2019). Influence of Deposition Temperature on the Phase Evolution of HfNbTiVZr High-Entropy Thin Films. Materials, 12(4), Article ID 587.
Open this publication in new window or tab >>Influence of Deposition Temperature on the Phase Evolution of HfNbTiVZr High-Entropy Thin Films
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2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 4, article id 587Article in journal (Refereed) Published
Abstract [en]

In this study, we show that the phase formation of HfNbTiVZr high-entropy thin films is strongly influenced by the substrate temperature. Films deposited at room temperature exhibit an amorphous microstructure and are 6.5 GPa hard. With increasing substrate temperature (room temperature to 275 degrees C), a transition from an amorphous to a single-phased body-centred cubic (bcc) solid solution occurs, resulting in a hardness increase to 7.9 GPa. A higher deposition temperature (450 degrees C) leads to the formation of C14 or C15 Laves phase precipitates in the bcc matrix and a further enhancement of mechanical properties with a peak hardness value of 9.2 GPa. These results also show that thin films follow different phase formation pathways compared to HfNbTiVZr bulk alloys.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
high-entropy alloys, physical vapour deposition (PVD), metallic glass
National Category
Metallurgy and Metallic Materials Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-380494 (URN)10.3390/ma12040587 (DOI)000460793300037 ()30781407 (PubMedID)
Funder
Swedish Research Council, 2018-04834
Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2019-03-28Bibliographically approved
Cedervall, J., Andersson, M. S., Iusan, D., Delczeg-Czirjak, E. K., Jansson, U., Nordblad, P. & Sahlberg, M. (2019). Magnetic and mechanical effects of Mn substitutions in AlFe2B2. Journal of Magnetism and Magnetic Materials, 482, 54-60
Open this publication in new window or tab >>Magnetic and mechanical effects of Mn substitutions in AlFe2B2
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2019 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 482, p. 54-60Article in journal (Refereed) Published
Abstract [en]

The mechanical and magnetic properties of the newly discovered MAB-phase class of materials based upon AlFe2B2 were investigated. The samples were synthesised from stoichiometric amounts of all constituent elements. X-ray diffraction shows that the main phase is orthorhombic with an elongated b-axis, similar to AlFe2B2. The low hardness and visual inspection of the samples after deformation indicate that these compounds are deformed via a delamination process. When substituting iron in AlFe2B2 with manganese, the magnetism in the system goes from being ferro- to antiferromagnetic via a disordered ferrimagnetic phase exhibited by AlFeMnB2. Density functional theory calculations indicate a weakening of the magnetic interactions among the transitions metal ions as iron is substituted by manganese in AlFe2B2. The Mn-Mn exchange interactions in AlMn2B2 are found to be very small.

National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-331787 (URN)10.1016/j.jmmm.2019.03.046 (DOI)000465553100010 ()
Funder
Swedish Research CouncilSwedish Energy Agency, 2017/11-55Swedish Energy Agency, 2018/1-34
Available from: 2017-10-19 Created: 2017-10-19 Last updated: 2019-06-14Bibliographically approved
Kryshtal, O., Kruk, A., Mao, F., Taher, M., Jansson, U. & Czyrska-Filemonowicz, A. (2019). Microstructure and phase composition of the Ag-Al film wear track: Through-thickness characterization by advanced electron microscopy. Archives of Metallurgy and Materials, 64(1), 251-256
Open this publication in new window or tab >>Microstructure and phase composition of the Ag-Al film wear track: Through-thickness characterization by advanced electron microscopy
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2019 (English)In: Archives of Metallurgy and Materials, ISSN 1733-3490, E-ISSN 2300-1909, Vol. 64, no 1, p. 251-256Article in journal (Refereed) Published
Abstract [en]

Analytical transmission electron microscopy has been applied to characterize the microstructure, phase and chemical composition of the Ag-Al wear track throughout its thickness down to the atomic level. Microscopy findings have been correlated with Ag-Al film tribological properties to understand the effect of the hexagonal solid solution phase on the tribological properties of this film. Ag-25Al (at.%) films have been produced by simultaneous magnetron sputtering of components in Ar atmosphere under 1 mTorr pressure and subjected to pin-on-disc tribological tests. It has been shown that hcp phase with (001) planes aligned parallel to the film surface dominates both in as-deposited and in tribofilm areas of the Ag-Al alloy film. Possible mechanisms of reduced friction in easily oxidized Ag-Al system are discussed and the mechanism based on readily shearing basal planes of the hcp phase is considered as the most probable one.

Place, publisher, year, edition, pages
POLSKA AKAD NAUK, POLISH ACAD SCIENCES, INST METALL & MATER SCI PAS, 2019
Keywords
Ag-Al alloy, TEM, EDX, hexagonal phase, electrical contact
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-381213 (URN)10.24425/amm.2019.126245 (DOI)000461713400036 ()
Available from: 2019-04-09 Created: 2019-04-09 Last updated: 2019-04-09Bibliographically approved
Mockute, A., Palisaitis, J., Nedfors, N., Berastegui, P., Broitman, E., Alling, B., . . . Rosen, J. (2019). Synthesis and characterization of (Ti1-xAlx)B2+Delta thin films from combinatorial magnetron sputtering. Thin Solid Films, 669, 181-187
Open this publication in new window or tab >>Synthesis and characterization of (Ti1-xAlx)B2+Delta thin films from combinatorial magnetron sputtering
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2019 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 669, p. 181-187Article in journal (Refereed) Published
Abstract [en]

(Ti1-xAlx)B2+Delta films with a lateral composition gradient of x = [0.30-0.66] and Delta = [0.07-1.22] were deposited on an Al2O3 wafer by dual magnetron sputtering at 400 degrees C from sintered TiB2 and AlB2 targets. Composition analysis indicates that higher Ti:Al ratios favor overstoichiometry in B and a reduced incorporation of O. Transmission electron microscopy reveals distinctly different microstructures of Ti- and Al-rich compositions, with formation of characteristic conical growth features for the latter along with a lower degree of crystallinity and significantly less tissue phase from B segregation at the grain boundaries. For Al-rich films, phase separation into Ti- and Al-rich diboride nanometer-size domains is observed and interpreted as surface-initiated spinodal decomposition. The hardness of the films ranges from 14 to 28 GPa, where the higher values were obtained for the Ti-rich regions of the metal boride.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2019
Keywords
Titanium aluminium diboride, Thin films, Combinatorial sputtering, Mechanical properties, Phase decomposition
National Category
Materials Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-372875 (URN)10.1016/j.tsf.2018.10.042 (DOI)000453405600026 ()
Funder
Knut and Alice Wallenberg Foundation, KAW 2015.0043Swedish Research Council, 330-2014-6336Swedish Research Council, 2016-04412Swedish Research Council, 642-2013-8020Swedish Foundation for Strategic Research
Available from: 2019-01-10 Created: 2019-01-10 Last updated: 2019-01-10Bibliographically approved
Pacheco, V., Lindwall, G., Karlsson, D., Cedervall, J., Fritze, S., Ek, G., . . . Jansson, U. (2019). Thermal Stability of the HfNbTiVZr High-Entropy Alloy. Inorganic Chemistry, 58(1), 811-820
Open this publication in new window or tab >>Thermal Stability of the HfNbTiVZr High-Entropy Alloy
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2019 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 58, no 1, p. 811-820Article in journal (Refereed) Published
Abstract [en]

The multicomponent alloy HfNbTiVZr has been described as a single-phase high-entropy alloy (HEA) in the literature, although some authors have reported that additional phases can form during annealing. The thermal stability of this alloy has therefore been investigated with a combination of experimental annealing studies and thermodynamic calculations using the CALPHAD approach. The thermodynamic calculations show that a single-phase HEA is stable above about 830 degrees C. At lower temperatures, the most stable state is a phase mixture of bcc, hcp, and a cubic C15 Laves phase. Annealing experiments followed by quenching confirm the results from thermodynamic calculations with the exception of the Laves phase structure, which was identified as a hexagonal C14 type instead of the cubic C15 type. Limitations of the applied CALPHAD thermodynamic description of the system could be an explanation for this discrepancy. As-synthesized HfNbTiVZr alloys prepared by arc-melting form a single-phase bcc HEA at room temperature. In situ annealing studies of this alloy show that additional phases start to form above 600 degrees C. This indicates that the observed HEA is metastable at room temperature and stabilized by a slow kinetics during cooling. X-ray diffraction analyses using different cooling rates and annealing times show that the phase transformations in this HEA are slow and that completely different phase compositions can be obtained depending on the annealing procedure. In addition, it has been shown that the sample preparation method (mortar grinding, heat treatment, etc.) has a significant influence on the collected diffraction patterns and therefore on the phase identification and analysis.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:uu:diva-375221 (URN)10.1021/acs.inorgchem.8b02957 (DOI)000455289000093 ()30525533 (PubMedID)
Funder
Swedish Foundation for Strategic Research
Available from: 2019-01-30 Created: 2019-01-30 Last updated: 2019-01-30Bibliographically approved
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