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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
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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
Åkerfeldt, P., Pederson, R. & Antti, M.-L. (2016). A fractographic study exploring the relationship between the low cycle fatigue and metallurgical properties of laser metal wire deposited Ti-6Al-4V (ed.). Paper presented at . International Journal of Fatigue, 87, 245-256
Open this publication in new window or tab >>A fractographic study exploring the relationship between the low cycle fatigue and metallurgical properties of laser metal wire deposited Ti-6Al-4V
2016 (English)In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 87, p. 245-256Article in journal (Refereed) Published
Abstract [en]

Additive manufacturing (AM) has achieved large attention within the aerospace industry mainly because of the possibility to lower the material and the manufacturing cost. For titanium alloys several AM techniques are available today. In the present paper, the focus has been on laser metal wire-deposition of Ti-6Al-4V. Walls were built and low cycle fatigue specimens were cut out in two orientations with respect to the deposition direction. An extensive fractographic evaluation was carried out after testing and the results indicated anisotropic behaviour at low strain ranges. Defects such as pores and lack of fusion (LoF) were observed and related to the fatigue life and specimen orientation. The LoF defects are regarded to have the most detrimental influence on the fatigue life, whilst the effect of pores was not as straightforward. Noteworthy in present study is that one large LoF defect did not influence the fatigue life, which is explained by the prevalence of the LoF defect in relation to the loading direction.

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-5610 (URN)10.1016/j.ijfatigue.2016.02.011 (DOI)000374615900026 ()2-s2.0-84958951831 (Scopus ID)3c23bc11-ab50-4499-8cb0-c65a627389a7 (Local ID)3c23bc11-ab50-4499-8cb0-c65a627389a7 (Archive number)3c23bc11-ab50-4499-8cb0-c65a627389a7 (OAI)
Note
Validerad; 2016; Nivå 2; 20160215 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Sefer, B., Gaddam, R., Rovira, J. J., Mateo, A., Antti, M.-L. & Pederson, R. (2016). Chemical milling effect on the low cycle fatigue properties of cast Ti-6Al-2Sn-4Zr-2Mo alloy (ed.). International Journal of Fatigue, 92(1), 193-202
Open this publication in new window or tab >>Chemical milling effect on the low cycle fatigue properties of cast Ti-6Al-2Sn-4Zr-2Mo alloy
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2016 (English)In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 92, no 1, p. 193-202Article in journal (Refereed) Published
Abstract [en]

The current research work presents the chemical milling effect on the low cycle fatigue properties of cast Ti-6Al-2Sn-4Zr-2Mo alloy. Chemical milling treatment is one of the final steps in manufacturing titanium alloy components that removes the brittle alpha-case layer formed during various thermal processes. The treatment includes immersion of the components in solutions containing hydrofluoric (HF) and nitric (HNO3) acids in relevant molar ratios. Although this treatment demonstrates advantages in handling components with complex net geometries, it may have detrimental effects on the surface, by introducing pitting and/or intergranular corrosion and thereby adversely affecting in particular the fatigue strength. The first series of specimens were tested in as-machined condition. Two more series were, prior to fatigue testing, subjected to 5 and 60 minutes chemical milling treatment. It was found that the fatigue lives were substantially decreased for the chemically treated specimens. The fractographic investigation of all mechanically tested samples revealed multiple fatigue crack initiation sites in the chemically milled samples. These cracks were located either at the prior beta grain boundary or the prior beta grain boundary triple joints. The prior beta grain boundaries were found to have deep ditch-like appearance which depth increased with increasing milling time. These ditch-like grain boundaries acts as stress raisers and thereby promote early fatigue crack initiation and thus lower fatigue life.

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-3804 (URN)10.1016/j.ijfatigue.2016.07.003 (DOI)000383930200019 ()2-s2.0-84978771831 (Scopus ID)1a417aff-661b-4192-bd0c-6380c8f83b53 (Local ID)1a417aff-661b-4192-bd0c-6380c8f83b53 (Archive number)1a417aff-661b-4192-bd0c-6380c8f83b53 (OAI)
Note

Validerad; 2016; Nivå 2; 20160706 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Sefer, B., Rovira, J. J., Mateo, A., Pederson, R. & Antti, M.-L. (2016). Evaluation of the bulk and alpha-case properties in Ti-6Al-4V at micro- and nano-metric length scale (ed.). In: (Ed.), V. Venkatesh; A.L. Pilchak; J.E. Allison; S. Ankem; R. Boyer; J. Christodoulou; H.L. Fraser; M.A. Imam; J. Kosaka; H.J. Rack; A. Chaterjee; A. Woodfield (Ed.), 13th World Conference on Titanium: August 16-20, 2015 * Manchester Grand Hyatt * San Diego, California (pp. 1619-1624). : John Wiley and Sons, Article ID 271.
Open this publication in new window or tab >>Evaluation of the bulk and alpha-case properties in Ti-6Al-4V at micro- and nano-metric length scale
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2016 (English)In: 13th World Conference on Titanium: August 16-20, 2015 * Manchester Grand Hyatt * San Diego, California / [ed] V. Venkatesh; A.L. Pilchak; J.E. Allison; S. Ankem; R. Boyer; J. Christodoulou; H.L. Fraser; M.A. Imam; J. Kosaka; H.J. Rack; A. Chaterjee; A. Woodfield, John Wiley and Sons , 2016, p. 1619-1624, article id 271Conference paper, Published paper (Refereed)
Abstract [en]

In the present study the hardness of individual alpha (α)-Ti grains in Ti-6Al-4V was measured by nanoindentation using Berkovich tip indenter. Additionally, alpha-case layer was induced by performing isothermal heat treatment at 700°C in air for 500 hours. The average hardness of the α-Ti grains found in the bulk material and in the alpha-case layer were 6.7 ± 0.7 GPa and 9.4 ± 1.4 GPa, respectively. The high hardness of the α-Ti grains in the alpha-case layer is due to solid solution strengthening caused by interstitial oxygen diffusion. The thickness of the developed alpha-case layer was estimated metallographically and compared with that measured from a hardness profile performed along the layer. Moreover, electron back-scattered diffraction was used to determine the local crystallographic orientation, the texture of the alloy microstructure, as well as phase fraction changes, where the nanoindentation measurements were performed.

Place, publisher, year, edition, pages
John Wiley and Sons, 2016
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-35257 (URN)9b6349dd-547a-4f04-83c8-b2775ccabe0d (Local ID)9b6349dd-547a-4f04-83c8-b2775ccabe0d (Archive number)9b6349dd-547a-4f04-83c8-b2775ccabe0d (OAI)
Note
Upprättat; 2016; 20160513 (birsef)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-03-05Bibliographically approved
Åkerfeldt, P., Antti, M.-L. & Pederson, R. (2016). Influence of microstructure on mechanical properties of laser metal wire-deposited Ti-6Al-4V (ed.). Materials Science & Engineering: A, 674, 428-437
Open this publication in new window or tab >>Influence of microstructure on mechanical properties of laser metal wire-deposited Ti-6Al-4V
2016 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 674, p. 428-437Article in journal (Refereed) Published
Abstract [en]

In the present paper laser metal wire deposition of Ti-6Al-4V has been studied and the mechanical properties evaluated. The yield strength, ultimate tensile strength and tensile elongation were all found to depend on the orientation of the specimens with respect to the deposition direction. Two orientations in the deposited material were evaluated in the study, perpendicular and parallel to the deposition direction. The specimens in the perpendicular orientation showed 25–33% higher elongation than the specimens parallel to the deposition direction. The parallel specimens on the other hand showed both higher (4%) ultimate tensile strength and higher (2–5%) yield strength. Furthermore, the anisotropic mechanical properties were correlated to the microstructural constituents of the specimens

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-4353 (URN)10.1016/j.msea.2016.07.038 (DOI)000383292800051 ()2-s2.0-84981309761 (Scopus ID)24a405e2-e758-444d-883f-256680ef6c42 (Local ID)24a405e2-e758-444d-883f-256680ef6c42 (Archive number)24a405e2-e758-444d-883f-256680ef6c42 (OAI)
Note

Validerad; 2016; Nivå 2; 20160823 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Lundbäck, A., Pederson, R., Hörnqvist Colliander, M., Brice, C., Steuwer, A., Heralic, A., . . . Lindgren, L.-E. (2016). Modeling and Experimental Measurement with Synchrotron Radiation of Residual Stresses in Laser Metal Deposited Ti-6Al-4V (ed.). In: (Ed.), Proceedings of the 13th World Conference on Titanium: . Paper presented at World Conference on Titanium : 16/08/2015 - 20/08/2015 (pp. 1279-1282).
Open this publication in new window or tab >>Modeling and Experimental Measurement with Synchrotron Radiation of Residual Stresses in Laser Metal Deposited Ti-6Al-4V
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2016 (English)In: Proceedings of the 13th World Conference on Titanium, 2016, p. 1279-1282Conference paper, Published paper (Refereed)
Abstract [en]

There are many challenges in producing aerospace components by additive manufacturing (AM). One of them is to keep the residual stresses and deformations to a minimum. Another one is to achieve the desired material properties in the final component. A computer model can be of great assistance when trying to reduce the negative effects of the manufacturing process. In this work a finite element model is used to predict the thermo-mechanical response during the AM-process. This work features a physically based plasticity model coupled with a microstructure evolution model for the titanium alloy Ti -6Al-4V. Residual stresses in AM components were measured non-destructively using high-energy synchrotron X-ray diffraction on beam line ID15A at the ESRF, Grenoble. The results are compared with FE model predictions of residual stresses. During the process, temperatures and deformations was continuously measured. The measured and computed thermal history agrees well. The result with respect to the deformations agrees well qualitatively. Meaning that the change in deformation in each sequence is well predicted but there is a systematic error that is summing so that the quantitative agreement is lost.

National Category
Other Materials Engineering
Research subject
Material Mechanics
Identifiers
urn:nbn:se:ltu:diva-31578 (URN)10.1002/9781119296126.ch216 (DOI)5cca2dff-a4b6-473d-8493-af82f50e4f0b (Local ID)9781119293668 (ISBN)9781119296126 (ISBN)5cca2dff-a4b6-473d-8493-af82f50e4f0b (Archive number)5cca2dff-a4b6-473d-8493-af82f50e4f0b (OAI)
Conference
World Conference on Titanium : 16/08/2015 - 20/08/2015
Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-03-05Bibliographically approved
Lundbäck, A., Pederson, R., Hörnqvist, M., Brice, C., Steuwer, A., Heralic, A., . . . Lindgren, L.-E. (2015). Modelling and Simulation of Metal Deposition on a Ti-6al-4v Plate (ed.). Paper presented at National Congress on Computational Mechanics : 26/07/2015 - 30/07/2015. Paper presented at National Congress on Computational Mechanics : 26/07/2015 - 30/07/2015.
Open this publication in new window or tab >>Modelling and Simulation of Metal Deposition on a Ti-6al-4v Plate
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2015 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

There are many challenges in producing aerospace components by metal deposition (MD). One of them is to keep the residual stresses and deformations to a minimum. Anotherone is to achieve the desired material properties in the final component. A computer model can be of great assistance when trying to reduce the negative effects of the manufacturing process. In this work a finite element model is used to predict the thermo-mechanical response during the MD-process. This work features a pysically based plasticity model coupled with a microstructure evolution model for the titanium alloy Ti-6Al-4V. A thermally driven microstructure model is used to derive the evolution of the non-equilibrium compositions of α-phases and β-phase. Addition of material is done by activation of elements. The method is taking large deformations into consideration and adjusts the shape and position of the activated elements. This is particularilly important when adding material onto thin and flexible structures. The FE-model can be used to evaluate the effect of different welding sequenses. Validation of the model is performed by comparing measured deformations, strains, residual stresses and temperatures with the computed result. The deformations, strains and temepratures are measured during the process. The deformations are measured with a LVDT-gauge at one location. The strains are measured with a strain gauge at the same location as the deformations. The temperature is measured at five locations, close to the weld and with an increasing distance of one millimeter between each thermo couple. The residual stresses in MD component were measured non-destructively using high-energy synchrotron X-ray diffraction on beam line ID15A at the ESRF, Grenoble.

National Category
Other Materials Engineering
Research subject
Material Mechanics; Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-31025 (URN)5109fb86-6304-481a-8d1c-a73f6794e237 (Local ID)5109fb86-6304-481a-8d1c-a73f6794e237 (Archive number)5109fb86-6304-481a-8d1c-a73f6794e237 (OAI)
Conference
National Congress on Computational Mechanics : 26/07/2015 - 30/07/2015
Note
Godkänd; 2015; 20160510 (andlun)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-03-05Bibliographically approved
Gaddam, R., Sefer, B., Pederson, R. & Antti, M.-L. (2015). Oxidation and alpha–case formation in Ti–6Al–2Sn–4Zr–2Mo alloy (ed.). Paper presented at . Materials Characterization, 99, 166-174
Open this publication in new window or tab >>Oxidation and alpha–case formation in Ti–6Al–2Sn–4Zr–2Mo alloy
2015 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 99, p. 166-174Article in journal (Refereed) Published
Abstract [en]

Isothermal heat treatments in ambient air were performed on wrought Ti–6Al–2Sn–4Zr–2Mo (Ti–6242) material at 500, 593 and 700 °C for times up to 500 hours. In presence of oxygen at elevated temperatures simultaneous reactions occurred in Ti–6242 alloy, which resulted in formation of an oxide scale and a layer with higher oxygen concentration (termed as alpha–case). Total weight gain analysis showed that there was a transition in the oxidation kinetics. At 500 °C, the oxidation kinetics obeyed cubic relationship up to 200 hours and thereafter changed to parabolic at prolonged exposure times. At 593 °C, it followed parabolic relationship. After heat treatment at 700 °C, the oxidation obeyed parabolic relationship up to 200 hours and thereafter changed to linear at prolonged exposure times. The observed transition is believed to be due to the differences observed in the oxide scale. The activation energy for parabolic oxidation was estimated to be 157 kJ/mol. In addition, alpha–case layer was evaluated using optical microscope, electron probe micro analyser and microhardness tester. The thickness of the alpha–case layer was found to be a function of temperature and time, increasing proportionally, and following parabolic relationship. The activation energy for formation of alpha–case layer was estimated to be 153 kJ/mol.

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-4759 (URN)10.1016/j.matchar.2014.11.023 (DOI)000350085900020 ()2-s2.0-84918826061 (Scopus ID)2bfd5cde-715d-4aab-b9f2-d582de42ab5f (Local ID)2bfd5cde-715d-4aab-b9f2-d582de42ab5f (Archive number)2bfd5cde-715d-4aab-b9f2-d582de42ab5f (OAI)
Note
Validerad; 2015; Nivå 2; 20141120 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Singh, G., Satyanarayana, D., Pederson, R., Datta, R. & Ramamurty, U. (2014). Enhancement in creep resistance of Ti-6Al-4 V alloy due to Boron addition (ed.). Paper presented at . Materials Science & Engineering: A, 597, 194-203
Open this publication in new window or tab >>Enhancement in creep resistance of Ti-6Al-4 V alloy due to Boron addition
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2014 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 597, p. 194-203Article in journal (Refereed) Published
Abstract [en]

The addition of B, up to about 0.1 wt.%, to Ti-6Al-4 V reduces its as-cast grain and colony sizes by an order of magnitude. In this paper, the creep resistance of this alloy modified with 0.06 and 0.11 wt.% B additions was investigated in the temperature range of 475–550 °C and compared with that of 0B alloy. Conventional dead-weight creep tests as well as stress relaxation tests were employed for this purpose. Experimental results show that the B addition enhances both elevated temperature strength and creep properties of Ti64, especially at the lower end of the temperatures investigated. The steady state creep rate in the alloy with 0.11 wt.% B was found to be an order of magnitude lower than that in the base alloy, and both the strain at failure as well as the time for rupture increases with the B content. These marked improvements in the creep resistance due to B addition to Ti64 were attributed primarily to the increased number of inter-phase interfaces – a direct consequence of the microstructural refinement that occurs with the B addition – that provide resistance to dislocation motion

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-7553 (URN)10.1016/j.msea.2013.12.078 (DOI)000332804800026 ()2-s2.0-84892651645 (Scopus ID)5f0841f8-4407-4153-9125-3d69aae10a03 (Local ID)5f0841f8-4407-4153-9125-3d69aae10a03 (Archive number)5f0841f8-4407-4153-9125-3d69aae10a03 (OAI)
Note
Validerad; 2014; 20140107 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Gaddam, R., Pederson, R., Hörnqvist, M. & Antti, M.-L. (2014). Fatigue crack growth behaviour of forged Ti-6Al-4V in gaseous hydrogen (ed.). Paper presented at . Corrosion Science, 78, 378-383
Open this publication in new window or tab >>Fatigue crack growth behaviour of forged Ti-6Al-4V in gaseous hydrogen
2014 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 78, p. 378-383Article in journal (Refereed) Published
Abstract [en]

Fatigue crack growth (FCG) tests were performed to evaluate the fatigue behaviour of forged Ti-6Al-4V in air and high-pressure gaseous hydrogen (15 MPa) at room temperature. The results indicate that the effect of gaseous hydrogen is dependent on the stress intensity factor (ΔK). The FCG rate was unaffected by hydrogen below a critical stress intensity, ΔK* ≈ 20 MPa√m. Above ΔK*, the FCG rate fluctuated and subsequently accelerated at higher ΔK values. The observed behaviour is attributed to the change in the fracture processes. A hypothesis is proposed that describes the FCG behaviour in gaseous hydrogen.

Keywords
titanium, SEM, hydrogen embrittlement, Materials science - Construction materials, Teknisk materialvetenskap - Konstruktionsmaterial
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-3036 (URN)10.1016/j.corsci.2013.08.009 (DOI)000329420900042 ()2-s2.0-84888007730 (Scopus ID)0ca240e9-a7f9-4ea3-a4e8-2917d631aade (Local ID)0ca240e9-a7f9-4ea3-a4e8-2917d631aade (Archive number)0ca240e9-a7f9-4ea3-a4e8-2917d631aade (OAI)
Note
Validerad; 2014; 20130818 (raggad)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-7675-7152

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