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Publikasjoner (10 av 65) Visa alla publikasjoner
Nilsson, E. A. ., Pettersson, L. & Antti, M.-L. (2019). Mn, Si and Ti in cast stainless steel at elevated temperature. Ironmaking & steelmaking, 46(8), 731-741
Åpne denne publikasjonen i ny fane eller vindu >>Mn, Si and Ti in cast stainless steel at elevated temperature
2019 (engelsk)Inngår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 46, nr 8, s. 731-741Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

ACI HH II is an austenitic castable stainless steel for high-temperature applications such as grates in a Grate-Kiln indurator. Eight different alloy compositions have been used to evaluate the oxide formation and the microstructural evolution during an isothermal heat treatment at 800°C with a holding time of 200 h in an atmosphere containing 20% O2–N2. Residual ferrite is transformed into sigma phase during the heat treatment while secondary carbides are precipitated in the austenite. Silicon will form a thinner oxide but will reduce its adherence to the steel. Additions of Ti are beneficial for the properties of the oxide layer as the oxide is well adherent and thinner, while additions of Mn increase the growth rate of the oxide and enhance the risk of growth stresses in the oxide. It is proposed that by combing the beneficial effects of both Ti and Si it is possible to suppress the malign effects of Mn additions.

sted, utgiver, år, opplag, sider
Taylor & Francis, 2019
Emneord
Grate-Kiln, stainless-steel, high temperature, microsegregation, Si, Mn, Ti
HSV kategori
Forskningsprogram
Materialteknik
Identifikatorer
urn:nbn:se:ltu:diva-67016 (URN)10.1080/03019233.2017.1405778 (DOI)000490481500005 ()
Merknad

Validerad;2019;Nivå 2;2019-10-09 (johcin)

Tilgjengelig fra: 2017-12-14 Laget: 2017-12-14 Sist oppdatert: 2019-11-06bibliografisk kontrollert
Neikter, M., Woracek, R., Maimaitiyili, T., Scheffzük, C., Strobl, M., Antti, M.-L., . . . Bjerkén, C. (2018). Alpha texture variations in additive manufactured Ti-6Al-4V investigated with neutron diffraction. Additive Manufacturing, 23, 225-234
Åpne denne publikasjonen i ny fane eller vindu >>Alpha texture variations in additive manufactured Ti-6Al-4V investigated with neutron diffraction
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2018 (engelsk)Inngår i: Additive Manufacturing, ISSN 2214-8604, Vol. 23, s. 225-234Artikkel i tidsskrift (Fagfellevurdert) Published
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].

sted, utgiver, år, opplag, sider
Elsevier, 2018
HSV kategori
Forskningsprogram
Materialteknik
Identifikatorer
urn:nbn:se:ltu:diva-70649 (URN)10.1016/j.addma.2018.08.018 (DOI)000453495500022 ()2-s2.0-85051782355 (Scopus ID)
Merknad

Validerad;2018;Nivå 2;2018-08-29 (andbra)

Tilgjengelig fra: 2018-08-29 Laget: 2018-08-29 Sist oppdatert: 2019-05-11bibliografisk kontrollert
Neikter, M., Forsberg, F., Pederson, R., Antti, M.-L., Åkerfeldt, P., Larsson, S., . . . Puyoo, G. (2018). Defect characterization of electron beam melted Ti-6Al-4V and Alloy 718 with X-ray microtomography. Aeronautics and Aerospace Open Access Journal, 2(3), 139-145
Åpne denne publikasjonen i ny fane eller vindu >>Defect characterization of electron beam melted Ti-6Al-4V and Alloy 718 with X-ray microtomography
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2018 (engelsk)Inngår i: Aeronautics and Aerospace Open Access Journal, ISSN 2576-4500, Vol. 2, nr 3, s. 139-145Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Electron beam melting (EBM) is emerging as a promising manufacturing process where metallic components are manufactured from three-dimensional (3D) computer aided design models by melting layers onto layers. There are several advantages with this manufacturing process such as near net shaping, reduced lead times and the possibility to decrease weight by topology optimization, aspects that are of interest for the aerospace industry. In this work two alloys, Ti-6Al-4V and Alloy 718, widely used within the aerospace industry were investigated with X-ray microtomography (XMT), to characterize defects such as lack of fusion (LOF) and inclusions. It was furthermore possible to view the macrostructure with XMT, which was compared to macrostructure images obtained by light optical microscopy (LOM). XMT proved to be a useful tool for defect characterization and both LOF and un-melted powder could be found in the two investigated samples. In the EBM built Ti-6Al-4V sample high density inclusions, believed to be composed of tungsten, were found. One of the high-density inclusions was found to be hollow, which indicate that the inclusion stems from the powder manufacturing process and not related with the EBM process. By performing defect analyses with the XMT software it was also possible to quantify the amount of LOF and un-melted powder in vol%. From the XMT-data meshes were produced so that finite element method (FEM) simulations could be performed. From these FEM simulations the significant impact of defects on the material properties was evident, as the defects led to high stress concentrations. It could moreover, with FEM, be shown that the as-built surface roughness of EBM material is of importance as high surface roughness led to increased stress concentrations.

sted, utgiver, år, opplag, sider
MedCrave Group, 2018
Emneord
X-ray tomography, Ti-6Al-4V, Alloy 718, defects and electron beam melting
HSV kategori
Forskningsprogram
Materialteknik; Hållfasthetslära; Experimentell mekanik
Identifikatorer
urn:nbn:se:ltu:diva-68924 (URN)10.15406/aaoaj.2018.02.00044 (DOI)
Tilgjengelig fra: 2018-05-28 Laget: 2018-05-28 Sist oppdatert: 2018-11-08bibliografisk kontrollert
Rubin, P., Larker, R., Navara, E. & Antti, M.-L. (2018). Graphite Formation and Dissolution in Ductile Irons and Steels Having High Silicon Contents: Solid-State Transformations. Metallography, Microstructure, and Analysis, 7(5), 587-595
Åpne denne publikasjonen i ny fane eller vindu >>Graphite Formation and Dissolution in Ductile Irons and Steels Having High Silicon Contents: Solid-State Transformations
2018 (engelsk)Inngår i: Metallography, Microstructure, and Analysis, ISSN 2192-9262, Vol. 7, nr 5, s. 587-595Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Graphite formation in the solid state is both in ductile cast irons and in steels strongly promoted by high silicon contents above 3 wt.% Si. The matrix microstructure in austempered ductile iron can be further refined by secondary graphite if the austenitization, quench, and isothermal transformation into ausferrite are preceded by an austenitization at a slightly higher temperature followed by quench to martensite, resulting in higher carbon content than being soluble at the second austenitization temperature. Hypoeutectoid steels with high silicon contents can be rapidly graphitized, causing recrystallization of surrounding ferrite due to plastic deformation making room for less dense graphite. In rolled steels, the interface between manganese sulfide and steel matrix is the most common nucleation site. Voids are formed when graphite is partly or completely dissolved during austenitization in succeeding hardening heat treatments, but the mechanical properties can still be good if the graphite particles dissolved into voids are below 20 µm. Graphitized Si-solution strengthened ferritic steels may perform similar to free-cutting steels but with improved mechanical properties.

sted, utgiver, år, opplag, sider
New York: Springer, 2018
Emneord
Graphitization High silicon iron High silicon steel Machinability Void formation Ausferrite
HSV kategori
Forskningsprogram
Materialteknik
Identifikatorer
urn:nbn:se:ltu:diva-71155 (URN)10.1007/s13632-018-0478-6 (DOI)000446639500008 ()2-s2.0-85054302639 (Scopus ID)
Merknad

Validerad;2018;Nivå 2;2018-10-09 (inah)

Tilgjengelig fra: 2018-10-09 Laget: 2018-10-09 Sist oppdatert: 2019-04-24bibliografisk kontrollert
Fargas, G., Roa, J., Sefer, B., Pedersen, R., Antti, M.-L. & Matteo, A. (2018). Influence of cyclic thermal treatments on the oxidation behavior of Ti-6Al-2Sn-4Zr-2Mo alloy. Materials Characterization, 145, 218-224
Åpne denne publikasjonen i ny fane eller vindu >>Influence of cyclic thermal treatments on the oxidation behavior of Ti-6Al-2Sn-4Zr-2Mo alloy
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2018 (engelsk)Inngår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 145, s. 218-224Artikkel i tidsskrift (Fagfellevurdert) Published
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.

sted, utgiver, år, opplag, sider
Elsevier, 2018
HSV kategori
Forskningsprogram
Materialteknik
Identifikatorer
urn:nbn:se:ltu:diva-70647 (URN)10.1016/j.matchar.2018.08.049 (DOI)000449449200023 ()2-s2.0-85052644847 (Scopus ID)
Merknad

Validerad;2018;Nivå 2;2018-09-03 (andbra)

Tilgjengelig fra: 2018-08-29 Laget: 2018-08-29 Sist oppdatert: 2018-11-29bibliografisk kontrollert
Ramanenka, D., Antti, M.-L., Gustafsson, G. & Jonsén, P. (2017). Characterization of high-alumina refractory bricks and modelling of hot rotary kiln behaviour. Engineering Failure Analysis, 79, 852-864
Åpne denne publikasjonen i ny fane eller vindu >>Characterization of high-alumina refractory bricks and modelling of hot rotary kiln behaviour
2017 (engelsk)Inngår i: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 79, s. 852-864Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Rotary kilns for iron-ore pellets production are highly dependent on a well-functioning refractory brick lining. To improve the long-term capability of the lining, in-situ observations of the bricks' performance are desired, however, the high process temperatures and the size of the kiln make it difficult to study the lining during operation. By using numerical simulations as a tool, some of the problems encountered by the brick lining can be studied. Knowing material properties of the refractory bricks as input in a numerical model is therefore necessary. However, material properties are poorly documented for this type of materials, especially, at elevated temperatures. In this work three commercial aluminasilicate bricks were tested in compression until failure for a temperature range of 25–1300 °C. The purpose was to evaluate compression strength and Young's modulus in compression of the fully burned bricks at a wide range of temperatures. The data was later used for modelling of a hot rotary kiln lined with bricks by using the finite element method, whereupon load state of the lining was evaluated at steady state after the expansion of the system. The objective of the numerical modelling was to investigate trustworthiness of the model and to give insight into the stress levels that can potentially arise. It was found that for all of the investigated brick types the compression strength increased with increased temperature, having a peak in the vicinity of 1000 °C. The maximum increase was between 50 and 150 % for the different brick types. After passing 1100 °C the compression strength rapidly and considerably decreased below its as-received compression strength. Young's modulus was measured to vary between 2 and 10 GPa in the range of up to 1000 °C. The numerical results indicate that severe boundary conditions (expansion of the lining is highly restricted) can potentially lead to compression stress of up to 34 MPa in the brick lining at steady state. However, at these boundary conditions the present tensile stress was only 0.5 MPa, while tensile stresses of close to 3 MPa could be observed in the lining with mild boundary conditions. The authors conclude that the created model is trustworthy and that it has high potential for being used as a tool in further investigations of the lining in hot state.

sted, utgiver, år, opplag, sider
Elsevier, 2017
HSV kategori
Forskningsprogram
Hållfasthetslära; Materialteknik
Identifikatorer
urn:nbn:se:ltu:diva-63536 (URN)10.1016/j.engfailanal.2017.04.038 (DOI)000405538800068 ()2-s2.0-85020181003 (Scopus ID)
Merknad

Validerad;2017;Nivå 2;2017-06-14 (rokbeg)

Tilgjengelig fra: 2017-05-26 Laget: 2017-05-26 Sist oppdatert: 2018-07-10bibliografisk kontrollert
Sefer, B., Dobryden, I., Almqvist, N., Pederson, R. & Antti, M.-L. (2017). Chemical Milling of Cast Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo Alloys in Hydrofluoric-Nitric Acid Solutions. Corrosion, 73(4), 394-407
Åpne denne publikasjonen i ny fane eller vindu >>Chemical Milling of Cast Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo Alloys in Hydrofluoric-Nitric Acid Solutions
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2017 (engelsk)Inngår i: Corrosion, ISSN 0010-9312, E-ISSN 1938-159X, Vol. 73, nr 4, s. 394-407Artikkel i tidsskrift (Fagfellevurdert) Published
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.

sted, utgiver, år, opplag, sider
NACE International, 2017
Emneord
atomic force microscopy, chemical milling/pickling, galvanic corrosion, linear polarization resistance, scanning Kelvin probe force microscopy, titanium alloys
HSV kategori
Forskningsprogram
Materialteknik; Experimentell fysik
Identifikatorer
urn:nbn:se:ltu:diva-62982 (URN)10.5006/2277 (DOI)000397433600008 ()2-s2.0-85020742117 (Scopus ID)
Merknad

Validerad; 2017; Nivå 2; 2017-04-11 (rokbeg)

Tilgjengelig fra: 2017-04-10 Laget: 2017-04-10 Sist oppdatert: 2018-12-14bibliografisk kontrollert
Nilsson, E. A. A., Pettersson, L. & Antti, M.-L. (2017). Effect of Si, Mn and Ti on High Temperature Resistance of a Travelling Grate in a Grate-Kiln Indurator. Ironmaking & steelmaking
Åpne denne publikasjonen i ny fane eller vindu >>Effect of Si, Mn and Ti on High Temperature Resistance of a Travelling Grate in a Grate-Kiln Indurator
2017 (engelsk)Inngår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812Artikkel i tidsskrift (Fagfellevurdert) Submitted
HSV kategori
Forskningsprogram
Processmetallurgi; Materialteknik
Identifikatorer
urn:nbn:se:ltu:diva-62159 (URN)
Tilgjengelig fra: 2017-02-24 Laget: 2017-02-24 Sist oppdatert: 2017-11-24
Neikter, M., Forsberg, F., Lycksam, H., Pederson, R. & Antti, M.-L. (2017). Microstructure and Defects in Additive Manufactured Titanium: a Comparison Between Microtomography and Optical Microscopy. In: : . Paper presented at 3rd International Conference on Tomography of Materials and Structures, Lund, Sweden, 26-30 June 2017.
Åpne denne publikasjonen i ny fane eller vindu >>Microstructure and Defects in Additive Manufactured Titanium: a Comparison Between Microtomography and Optical Microscopy
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2017 (engelsk)Konferansepaper, Oral presentation with published abstract (Annet vitenskapelig)
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 showthat both techniqueshave theirpros and cons:microtomography is the preferred choicefor defect detectionby analysing the full 3D sample volume, while light optical microscopy is better for analysing finer details in 2D.

HSV kategori
Forskningsprogram
Materialteknik; Strömningslära
Identifikatorer
urn:nbn:se:ltu:diva-65063 (URN)
Konferanse
3rd International Conference on Tomography of Materials and Structures, Lund, Sweden, 26-30 June 2017
Tilgjengelig fra: 2017-08-14 Laget: 2017-08-14 Sist oppdatert: 2018-04-25bibliografisk kontrollert
Neikter, M., Pederson, R., Åkerfeldt, P. & Antti, M.-L. (2017). Microstructure characterisation of Ti-6Al-4V from different additive manufacturing processes. Paper presented at International Materials Research Meeting in the Greater Region: "Current Trends in the Characterisation of Materials and Surface Modification", Saarland University, Saarbrücken, Germany, 6–7 April 2017. IOP Conference Series: Materials Science and Engineering, 258, Article ID 012007.
Åpne denne publikasjonen i ny fane eller vindu >>Microstructure characterisation of Ti-6Al-4V from different additive manufacturing processes
2017 (engelsk)Inngår i: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 258, artikkel-id 012007Artikkel i tidsskrift (Fagfellevurdert) Published
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.

sted, utgiver, år, opplag, sider
Institute of Physics (IOP), 2017
HSV kategori
Forskningsprogram
Materialteknik
Identifikatorer
urn:nbn:se:ltu:diva-66341 (URN)10.1088/1757-899X/258/1/012007 (DOI)2-s2.0-85035102621 (Scopus ID)
Konferanse
International Materials Research Meeting in the Greater Region: "Current Trends in the Characterisation of Materials and Surface Modification", Saarland University, Saarbrücken, Germany, 6–7 April 2017
Merknad

Konferensartikel i tidskrift

Tilgjengelig fra: 2017-11-01 Laget: 2017-11-01 Sist oppdatert: 2018-06-12bibliografisk kontrollert
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0003-3661-9262