Change search
Link to record
Permanent link

Direct link
BETA
Publications (10 of 64) Show all publications
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
Open this publication in new window or tab >>Alpha texture variations in additive manufactured Ti-6Al-4V investigated with neutron diffraction
Show others...
2018 (English)In: Additive Manufacturing, ISSN 2214-8604, Vol. 23, p. 225-234Article in journal (Refereed) 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].

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-70649 (URN)10.1016/j.addma.2018.08.018 (DOI)000453495500022 ()2-s2.0-85051782355 (Scopus ID)
Note

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

Available from: 2018-08-29 Created: 2018-08-29 Last updated: 2019-04-02Bibliographically approved
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
Open this publication in new window or tab >>Defect characterization of electron beam melted Ti-6Al-4V and Alloy 718 with X-ray microtomography
Show others...
2018 (English)In: Aeronautics and Aerospace Open Access Journal, ISSN 2576-4500, Vol. 2, no 3, p. 139-145Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
MedCrave Group, 2018
Keywords
X-ray tomography, Ti-6Al-4V, Alloy 718, defects and electron beam melting
National Category
Metallurgy and Metallic Materials Other Materials Engineering Fluid Mechanics and Acoustics Applied Mechanics
Research subject
Engineering Materials; Solid Mechanics; Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-68924 (URN)10.15406/aaoaj.2018.02.00044 (DOI)
Available from: 2018-05-28 Created: 2018-05-28 Last updated: 2018-11-08Bibliographically approved
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
Open this publication in new window or tab >>Graphite Formation and Dissolution in Ductile Irons and Steels Having High Silicon Contents: Solid-State Transformations
2018 (English)In: Metallography, Microstructure, and Analysis, ISSN 2192-9262, Vol. 7, no 5, p. 587-595Article in journal (Refereed) 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.

Keywords
Graphitization High silicon iron High silicon steel Machinability Void formation Ausferrite
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-71155 (URN)10.1007/s13632-018-0478-6 (DOI)000446639500008 ()2-s2.0-85054302639 (Scopus ID)
Note

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

Available from: 2018-10-09 Created: 2018-10-09 Last updated: 2018-11-21Bibliographically approved
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
Open this publication in new window or tab >>Influence of cyclic thermal treatments on the oxidation behavior of Ti-6Al-2Sn-4Zr-2Mo alloy
Show others...
2018 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 145, p. 218-224Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-70647 (URN)10.1016/j.matchar.2018.08.049 (DOI)000449449200023 ()2-s2.0-85052644847 (Scopus ID)
Note

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

Available from: 2018-08-29 Created: 2018-08-29 Last updated: 2018-11-29Bibliographically approved
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
Open this publication in new window or tab >>Characterization of high-alumina refractory bricks and modelling of hot rotary kiln behaviour
2017 (English)In: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 79, p. 852-864Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Applied Mechanics Other Materials Engineering
Research subject
Solid Mechanics; Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-63536 (URN)10.1016/j.engfailanal.2017.04.038 (DOI)000405538800068 ()2-s2.0-85020181003 (Scopus ID)
Note

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

Available from: 2017-05-26 Created: 2017-05-26 Last updated: 2018-07-10Bibliographically approved
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
Open this publication in new window or tab >>Chemical Milling of Cast Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo Alloys in Hydrofluoric-Nitric Acid Solutions
Show others...
2017 (English)In: Corrosion, ISSN 0010-9312, E-ISSN 1938-159X, Vol. 73, no 4, p. 394-407Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
NACE International, 2017
Keywords
atomic force microscopy, chemical milling/pickling, galvanic corrosion, linear polarization resistance, scanning Kelvin probe force microscopy, titanium alloys
National Category
Other Materials Engineering Other Physics Topics
Research subject
Engineering Materials; Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-62982 (URN)10.5006/2277 (DOI)000397433600008 ()2-s2.0-85020742117 (Scopus ID)
Note

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

Available from: 2017-04-10 Created: 2017-04-10 Last updated: 2018-12-14Bibliographically approved
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
Open this publication in new window or tab >>Effect of Si, Mn and Ti on High Temperature Resistance of a Travelling Grate in a Grate-Kiln Indurator
2017 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812Article in journal (Refereed) Submitted
National Category
Metallurgy and Metallic Materials Mineral and Mine Engineering Other Materials Engineering
Research subject
Process Metallurgy; Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-62159 (URN)
Available from: 2017-02-24 Created: 2017-02-24 Last updated: 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.
Open this publication in new window or tab >>Microstructure and Defects in Additive Manufactured Titanium: a Comparison Between Microtomography and Optical Microscopy
Show others...
2017 (English)Conference paper, Oral presentation with published abstract (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 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.

National Category
Metallurgy and Metallic Materials Other Materials Engineering Fluid Mechanics and Acoustics
Research subject
Engineering Materials; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-65063 (URN)
Conference
3rd International Conference on Tomography of Materials and Structures, Lund, Sweden, 26-30 June 2017
Available from: 2017-08-14 Created: 2017-08-14 Last updated: 2018-04-25Bibliographically approved
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.
Open this publication in new window or tab >>Microstructure characterisation of Ti-6Al-4V from different additive manufacturing processes
2017 (English)In: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 258, article id 012007Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2017
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-66341 (URN)10.1088/1757-899X/258/1/012007 (DOI)2-s2.0-85035102621 (Scopus ID)
Conference
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
Note

Konferensartikel i tidskrift

Available from: 2017-11-01 Created: 2017-11-01 Last updated: 2018-06-12Bibliographically approved
Nilsson, E., Tegman, R. & Antti, M.-L. (2017). Thermal cycling of grate-link material for iron ore pelletising process (ed.). Ironmaking & steelmaking, 44(4), 269-280
Open this publication in new window or tab >>Thermal cycling of grate-link material for iron ore pelletising process
2017 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 44, no 4, p. 269-280Article in journal (Refereed) Published
Abstract [en]

A test-rig for thermal cycling has been developed to investigate the mechanisms behind some of the damages done to a grate-link in a pelletising indurator for iron ore pellets. The results from the test-rig were compared with the degradation of grate-links that had been in service for 8 months in the indurator. The damages on the grate-links induced both in the test-rig and at service were defined as internal oxidation which facilitated propagation of intergranular stress corrosion cracking (IGSCC). Internal oxidation was initiated by spallation or removal of the oxide layers. The test-rig was able to successfully perform a lab-scale simulation of the degradation experienced in the indurator. Thermal cycling was applied to plate-formed specimens by constraining their thermal elongation to form bending and thereby stimulate the mechanisms of spallation and sensibilisation to IGSCC by internal oxidation.

Place, publisher, year, edition, pages
Taylor & Francis, 2017
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-8244 (URN)10.1080/03019233.2016.1210404 (DOI)000396722800005 ()2-s2.0-84980010123 (Scopus ID)6b903639-c677-4a13-93f4-39130abbb133 (Local ID)6b903639-c677-4a13-93f4-39130abbb133 (Archive number)6b903639-c677-4a13-93f4-39130abbb133 (OAI)
Note

Validerad; 2017; Nivå 2; 2017-03-22 (rokbeg)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-11-19Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3661-9262

Search in DiVA

Show all publications