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Segersäll, Mikael
Publications (10 of 16) Show all publications
Segersäll, M., Leidermark, D. & Moverare, J. (2015). Influence of crystal orientation on the thermomechanical fatigue behaviour in a single-crystal superalloy. Materials Science & Engineering: A, 623(19), 68-77
Open this publication in new window or tab >>Influence of crystal orientation on the thermomechanical fatigue behaviour in a single-crystal superalloy
2015 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 623, no 19, p. 68-77Article in journal (Refereed) Published
Abstract [en]

In this study, the influuence from crystal orientation on the thermomehanical fatigue (TMF) behaviour of the recently developed single-rystal superalloy STAL-15 is considered, both from an experimental and a nite element (FE) perspective. Experimental results show that there is a strong inuence from the elastic stiffness, with respect to the loading direction, on the TMF life. However, the results also indicate that the number of active slip planes duringdeformation inuence the TMF life, where specimens with a higher number of active slip planes are favoured compared to specimens with fewer active slip planes. The higher number of active slip planes results in a more widespread deformation compared to a more conentrated deformation when only one slip plane is active. Deformation bands with smeared and elongated  γ-precipitates together with deformation twinning were found to be major deformation mechanisms, where the twins primarily were observed in specimens with several active slip planes. From an FE-perspective, therystal orientation with respect to the loading direction is quantied and adopted into a framework which makes it possible to describe the internal crystallographic arrangement and its entities in a material model. Further, a material model which incorporates the crystalorientation is able to predict the number of slip planes observed from microstructural observations, as well as the elasticstiness of the material with respect to the loading direction.

Place, publisher, year, edition, pages
Elsevier, 2015
Keywords
Single-crystal superalloy, Crystal orientation dependence, Thermome hanical fatigue, Deformation mechanisms, Finite element
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-111639 (URN)10.1016/j.msea.2014.11.026 (DOI)000349063100009 ()
Note

On the day of the defence day the status of this article was Manuscript.

The work has been financially supported by Siemens Industrial Turbomachinery AB in Finspang, Sweden, and the Swedish Energy Agency, via the Research Consortium of Materials Technology for Thermal Energy Processes, Grant no. KME-702. In addition, the support from the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU #2009-00971) is also acknowledged.

Available from: 2014-10-27 Created: 2014-10-27 Last updated: 2017-12-05Bibliographically approved
Segersäll, M., Calmunger, M., Norman, V. & Fredriksson, C. (2015). Student Reactions to CES EduPack in an Undergraduate Materials Selection Course. In: : . Paper presented at Materials Education Symposium Cambridge April 9-10, 2015 (pp. 1-1).
Open this publication in new window or tab >>Student Reactions to CES EduPack in an Undergraduate Materials Selection Course
2015 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-115778 (URN)
Conference
Materials Education Symposium Cambridge April 9-10, 2015
Available from: 2015-03-19 Created: 2015-03-19 Last updated: 2015-04-02
Segersäll, M., Kontis, P., Pedrazzini, S., Bagot, P. A. .., Moody, M. P., Moverare, J. & Reed, R. C. (2015). Thermal-­Mechanical Fatigue Behaviour of a New Single Crystal Superalloy: Effects of Si and Re Alloying. Acta Materialia, 95, 456-467
Open this publication in new window or tab >>Thermal-­Mechanical Fatigue Behaviour of a New Single Crystal Superalloy: Effects of Si and Re Alloying
Show others...
2015 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 95, p. 456-467Article in journal (Refereed) Published
Abstract [en]

The mechanical behaviour of a new single crystal superalloy suitable for power generation applications is considered. Effects of alloying with either Si or Re are elucidated. Out-of-phase thermal-mechanical fatigue is emphasised, although to clarify the effects arising some static creep deformation tests are also carried out. A significant Si-effect is found: a modest addition of 0.25 wt. % Si increases the TMF life by a factor of 2. Thinner deformation bands which traverse the γ'-phase are promoted by Si alloying, with a concomitant greater resistance to recrystallization and cracking along them. Alloying with Re, whilst improving the creep behaviour more markedly than Si, does not have such a strong effect on TMF life. The results provide insights into the composition/performance relationships relevant to the TMF performance of single crystal superalloys.

Place, publisher, year, edition, pages
Elsevier, 2015
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-111640 (URN)10.1016/j.actamat.2015.03.060 (DOI)000358626200046 ()
Note

On the day of the defence date the status of this article was Manuscript.

The work has been supported financially by Siemens Industrial Turbomachinery AB in Finspang, Sweden and the Swedish Energy Agency, via the Research Consortium of Materials Technology for Thermal Energy Processes, Grant No. KME-702. In addition, the support from the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU #2009-00971) is also acknowledged. Funding from the Engineering and Physical Sciences Research Council (EPSRC) of the UK is acknowledged under Grant EP/J013501/1 'Multifunctional High Performance Alloys for Extreme Environments'.

Available from: 2014-10-27 Created: 2014-10-27 Last updated: 2017-12-05Bibliographically approved
Segersäll, M., Moverare, J. J., Leidermark, D. & Simonsson, K. (2014). Creep and Stress Relaxation Anisotropy of a Single-Crystal Superalloy. Metallurgical and Materials Transactions. A, 45(5), 2532-2544
Open this publication in new window or tab >>Creep and Stress Relaxation Anisotropy of a Single-Crystal Superalloy
2014 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 45, no 5, p. 2532-2544Article in journal (Refereed) Published
Abstract [en]

In this study, the TMF stress relaxation and creep behavior at 1023 K and 1223 K (750 °C and 950 °C) have been investigated for a Ni-based single-crystal superalloy. Specimens with three different crystal orientations along their axes were tested; 〈001〉, 〈011〉, and 〈111〉, respectively. A highly anisotropic behavior during TMF stress relaxation was found where the 〈111〉 direction significantly shows the worst properties of all directions. The TMF stress relaxation tests were performed in both tension and compression and the results indicate a clear tension/compression asymmetry for all directions where the greatest asymmetry was observed for the 〈001〉 direction at 1023 K (750 °C); here the creep rate was ten times higher in compression than tension. This study also shows that TMF cycling seems to influence the creep rate during stress relaxation temporarily, but after some time it decreases again and adapts to the pre-unloading creep rate. Creep rates from the TMF stress relaxation tests are also compared to conventional constant load creep rates and a good agreement is found.

Place, publisher, year, edition, pages
Springer, 2014
Keywords
Single-crystal superalloy, thermomechanical fatigue, creep, stress relaxation, deformation mechanism
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:liu:diva-89949 (URN)10.1007/s11661-014-2198-0 (DOI)000334428000026 ()
Note

On the day of the defense data of the Licentiate Thesis the status of this article was Manuscript.

Available from: 2013-03-12 Created: 2013-03-12 Last updated: 2017-12-06Bibliographically approved
Segersäll, M., Moverare, J., Leidermark, D. & Johansson, S. (2014). In- and Out-of Phase Thermomechanical Fatigue of a Ni-Based Single-Crystal Superalloy. In: J. Y. Guédou and J. Choné (Ed.), 2014 EUROSUPERALLOYS 2014 – 2nd European Symposium on Superalloys and their Applications: . Paper presented at EUROSUPERALLOYS 2014 – 2nd European Symposium on Superalloys and their Applications, 12-16 May 2014, Giens, France (pp. Article no. 19003). EDP Sciences, 14
Open this publication in new window or tab >>In- and Out-of Phase Thermomechanical Fatigue of a Ni-Based Single-Crystal Superalloy
2014 (English)In: 2014 EUROSUPERALLOYS 2014 – 2nd European Symposium on Superalloys and their Applications / [ed] J. Y. Guédou and J. Choné, EDP Sciences, 2014, Vol. 14, p. Article no. 19003-Conference paper, Published paper (Refereed)
Abstract [en]

In this study, the difference between in-phase (IP) and out-of-phase (OP) thermomechanical fatigue (TMF) cycling from 100 to 750 °C has been investigated for the Ni-based single-crystal superalloy MD2. In addition, two different crystal orientations were studied, the ⟨001⟩ and ⟨011⟩ orientations respectively. When comparing IP and OP TMF lives, a strain range dependency is found for the ⟨001⟩ direction. For high strain ranges, IP cycling leads to a higher number of cycles to failure compared to OP. However at lower strain ranges, OP cycling leads to a higher number of cycles to failure compared to IP. Microstructure investigation shows that for the ⟨001⟩ direction, deformation twinning within the γ/γ′-microstructure is much more pronounced during OP conditions compared to IP. However for the ⟨011⟩ direction, the opposite is observed; twinning is more pronounced during IP TMF. From the microstructure investigation it is also visible that intersections between twins seems to trigger formation of TCP phases and recrystallization. These intersections also work as initiation points for TMF damage.

Place, publisher, year, edition, pages
EDP Sciences, 2014
Series
MATEC Web of Conferences, ISSN 2261-236X ; 14
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-111066 (URN)10.1051/matecconf/20141419003 (DOI)000351930400073 ()
Conference
EUROSUPERALLOYS 2014 – 2nd European Symposium on Superalloys and their Applications, 12-16 May 2014, Giens, France
Available from: 2014-10-06 Created: 2014-10-06 Last updated: 2016-05-26Bibliographically approved
Segersäll, M., Moverare, J., Leidermark, D. & Simonsson, K. (2014). Low-Cycle Fatigue Behaviour of a Ni-Based Single-Crystal Superalloy. Paper presented at Fatigue 2014, 11th International Fatigue Congress, Melbourne Cricket Ground, Melbourne, Australia, 2-7 March 2014.. Advanced Materials Research, 891-892, 416-421
Open this publication in new window or tab >>Low-Cycle Fatigue Behaviour of a Ni-Based Single-Crystal Superalloy
2014 (English)In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 891-892, p. 416-421Article in journal (Refereed) Published
Abstract [en]

In this study, low-cycle fatigue (LCF) tests at 500 degrees C in the < 001 >, < 011 > and < 111 > directions have been performed for the Ni-based single-crystal superalloy MD2. All tests were carried out in strain control with R-is an element of = -1. The < 001 > direction has the lowest stiffness of the three directions and also shows the best fatigue properties in this study followed by the < 011 > and < 111 > directions, respectively. It is well recognised that Ni-based single-crystal superalloys show a tension/compression asymmetry in yield strength and this study shows that a tension/compression asymmetry is also present during LCF conditions. At mid-life, the < 001 > direction generally has a higher stress in tension than in compression, while the opposite is true for the < 011 > direction. For the < 111 > direction the asymmetry is found to be strain range dependent. The < 011 > and < 111 > directions show a cyclic hardening behaviour when comparing cyclic stress-strain curves with monotonic stress-strain curves. In addition, the < 011 > and < 111 > directions show a serrated yielding behaviour for a number of cycles while the yielding of the < 001 > direction is more stable.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2014
Keywords
Ni-based single-crystal superalloy, LCF, tension/compression asymmetry, serrated yielding
National Category
Engineering and Technology Materials Engineering
Identifiers
urn:nbn:se:liu:diva-104750 (URN)10.4028/www.scientific.net/AMR.891-892.416 (DOI)000337767700064 ()
Conference
Fatigue 2014, 11th International Fatigue Congress, Melbourne Cricket Ground, Melbourne, Australia, 2-7 March 2014.
Available from: 2014-02-25 Created: 2014-02-25 Last updated: 2017-12-05
Leidermark, D. & Segersäll, M. (2014). Modelling of Thermomechanical Fatigue Stress Relaxation in a Single-Crystal Nickel-Base Superalloy. Computational materials science, 90, 61-70
Open this publication in new window or tab >>Modelling of Thermomechanical Fatigue Stress Relaxation in a Single-Crystal Nickel-Base Superalloy
2014 (English)In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 90, p. 61-70Article in journal (Refereed) Published
Abstract [en]

The thermomechanical fatigue (TMF) stress relaxation of the single-crystal nickel-base superalloy MD2 has been analysed and modelled in this paper. In-phase and out-of-phase TMF experiments in the nominal [001],[011] and [111] crystal orientations have been performed. The TMF cycle consists of two loadings each with a 100 h long hold-time. A simple crystallographic creep model, based on Norton’s creep law, has been developed and used in conjunction with a crystal plasticity model. The model takes anisotropy and tension/compression asymmetry into account, where the anisotropic behaviour is based on the crystallographic stress state. The values of the creep parameters in the anisotropic expression were determined by inverse modelling of the conducted TMF experiments, a parameter optimisation were performed. The developed model predicts the stress relaxation seen in the TMF experiments with good correlation.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
single-crystal superalloy, thermomechanical fatigue, creep, stress relaxation, anisotropy, parameter optimisation
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-107983 (URN)10.1016/j.commatsci.2014.04.009 (DOI)000336656200009 ()
Available from: 2014-06-24 Created: 2014-06-24 Last updated: 2017-12-05Bibliographically approved
Leidermark, D., Segersäll, M., Moverare, J. & Simonsson, K. (2014). Modelling of TMF Crack Initiation in Smooth Single-Crystal Superalloy Specimens. In: : . Paper presented at 11th International Fatigue Congress (Fatigue 2014), 2-7 Mars 2014, Melbourne, Australien (pp. 1283-1288). Trans Tech Publications Inc., 891-892
Open this publication in new window or tab >>Modelling of TMF Crack Initiation in Smooth Single-Crystal Superalloy Specimens
2014 (English)Conference paper, Published paper (Refereed)
Abstract [en]

In this paper the TMF crack initiation behaviour of the single-crystal nickel-base superalloyMD2 is investigated and modelled. TMF tests were performed in both IP and OP for varying mechanicalstrain ranges in the [001] crystallographic direction until TMF crack initiation was obtained. Acrystal plasticity-creep model was used in conjunction with a critical-plane approach, to evaluate thenumber of cycles to TMF crack initiation. The critical-plane model was evaluated and calibrated ata stable TMF cycle, where the effect of the stress relaxation had attenuated. This calibrated criticalplanemodel is able to describe the TMF crack initiation, taking tension/compression asymmetry aswell as stress relaxation anisotropy into account, with good correlation to the real fatigue behaviour.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2014
Keywords
single-crystal superalloy, thermomechanical fatigue, crack initiation, stress relaxation, creep, anisotropy, tension/compression asymmetry
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-105336 (URN)10.4028/www.scientific.net/AMR.891-892.1283 (DOI)000337767700198 ()
Conference
11th International Fatigue Congress (Fatigue 2014), 2-7 Mars 2014, Melbourne, Australien
Available from: 2014-03-18 Created: 2014-03-18 Last updated: 2015-03-06Bibliographically approved
Segersäll, M. (2014). On Thermomechanical Fatigue of Single-Crystal Superalloys. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>On Thermomechanical Fatigue of Single-Crystal Superalloys
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Thanks to their excellent mechanical and chemical properties at temperatures up to 1000 °C, nickel-based superalloys are used in critical components in high-temperature applications such as gas turbines and aero engines. One of the most critical components in a gas turbine is the turbine blade, and to improve the creep and fatigue properties of this component, it is sometimes cast in single-crystal form rather than in the more conventional poly-crystalline form. Gas turbines are most commonly used for power generation and the turbine efficiency is highly dependent on the performance of the superalloys.

Today, many gas turbines are used as a complement for renewable energy sources, for example when the wind is not blowing or when the sun is not shining. This means that the turbine runs differently compared to earlier, when it ran for longer time periods with a lower number of start-ups and shut-downs. This new way of running the turbine, with an increased number of start-ups and shut-downs, results in new conditions for critical components, and one way to simulate these conditions is to perform thermomechanical fatigue (TMF) testing in the laboratory. During TMF, both mechanical strain and temperature are cycled at the same time, and one fatigue cycle corresponds to the conditions experienced by the turbine blade during one start-up and shutdown of the turbine engine.

In the work leading to this PhD thesis, TMF testing of single-crystal superalloys was first performed in the laboratory and this was then followed microstructure investigations to study the occurring deformation and damage mechanisms. Specimens with different crystallographic directions have been tested in order to investigate the anisotropic behaviour shown by these materials. Results show a significant orientation dependence during TMF, in which specimens with a low elastic stiffness perform better. However, it is also shown that specimens with a higher number of active slip planes perform better during TMF compared to specimens with less active slip systems. This is because a higher number of active slip systems results in a more widespread deformation and seems to be beneficial for the TMF life. Further, microscopy shows that the deformation during TMF is localised to several deformation bands and that different deformation and damage mechanisms prevail according to in which crystal orientation the material is loaded. Deformation twinning is shown to be a major deformation mechanism during TMF, and the interception of twins seems to trigger recrystallization. This work also studies the effects of alloying a single-crystal superalloy with Si or Re, and results show a significant Si-effect where the TMF life increases by a factor of 2 when Si is added to the alloy.

Finally, this research results in an increased knowledge of the mechanical response as well as a deeper understanding of the deformation and damage mechanisms that occur in single-crystal superalloys during TMF. It is believed that in the long-term, this can contribute to a more efficient and reliable power generation by gas turbines.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. p. 83
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1626
National Category
Materials Engineering Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-111643 (URN)10.3384/diss.diva-111643 (DOI)978-91-7519-211-6 (ISBN)
Public defence
2014-11-28, ACAS, Hus A, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2014-10-27 Created: 2014-10-27 Last updated: 2014-10-27Bibliographically approved
Calmunger, M. & Segersäll, M. (2014). Using the Student Diversity as a Strength in a Material Selection Course. In: : . Paper presented at 6th International Materials Education Symposium, University of Cambridge, 10-11 April 2014. (pp. 1).
Open this publication in new window or tab >>Using the Student Diversity as a Strength in a Material Selection Course
2014 (English)Conference paper, Poster (with or without abstract) (Other (popular science, discussion, etc.))
National Category
Engineering and Technology Materials Engineering
Identifiers
urn:nbn:se:liu:diva-106065 (URN)
Conference
6th International Materials Education Symposium, University of Cambridge, 10-11 April 2014.
Note

The background of this study is to highlight the task for a university teacher to maintain a high academic standard with an increased number of students and the fact that students have a different pre-knowledge. In our case, this is having both mechanical engineering students and engineering design students in a 4th year university material selection course. Generally, those two groups tend to approach a material selection problem in different ways. To use this diversity as a strength, we try to integrate the different student groups with each other in order to make a material selection with different inputs. In addition, if the students can see their learning as a function of their activity during the course this can also motivate the students to learn from each other. Hence, our task as teachers is therefore to supply teaching/learning activities that are active and stimulating for the students.

 

Due to a large number of students, home assignments interconnected to the course objectives are to be solved in small groups. By working in small groups, the work is peer-controlled and therefore also increases the student influence of the learning process. A peer-controlled project at the end of the course is also introduced where the students are able to use their pre-knowledge from bachelor studies as well as the knowledge gained from the course. The aim is to maintain a high academic standard by having a student centred learning throughout the course as well as using the diversity as something positive. 

Available from: 2014-04-22 Created: 2014-04-22 Last updated: 2014-04-28
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