Quantitative analysis of the microstructure in NiTi wires by Synchrotron X-ray diffraction: An approach to the cause of the Two Way Shape Memory Effect.
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| Title: | Quantitative analysis of the microstructure in NiTi wires by Synchrotron X-ray diffraction: An approach to the cause of the Two Way Shape Memory Effect. |
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| Authors: | Urbina, C.1 cristina.urbina@urv.cat, Gispert-Guirado, F.2, Ferrando, F.1, De la Flor, S.1 |
| Source: | Journal of Alloys & Compounds. Jul2017, Vol. 712, p833-847. 15p. |
| Subjects: | Shape memory alloys, Nickel-titanium alloys, Microstructure, Wire, X-ray diffraction |
| Abstract: | To understand the complex behaviour of the NiTi shape memory alloys, the use of advanced characterization techniques as Synchrotron X-ray diffraction, becomes more and more necessary. In this paper, this technique was performed in heat-treated, thermally cycled at zero stress and two-way memory trained NiTi wires to evaluate through microstrain and retained martensite which is the predominant micro-mechanism that cause the Two Way Shape Memory Effect. The microstructural effects in the structure of the Austenite by thermal and training methods were quantified separately for each NiTi sample, allowing us to calculate how much of the accumulated microstrain in the Austenite phase is due to the increment in density of dislocations and how much is consequence of the decrease in crystallite size. To achieve this, two different methodologies were used. The mean microstrain and shift index were calculated by analysing the whole diffractogram with the Rietveld method and the Double-Voigt Approach. The individual peak shift and the peak broadening of the Austenite phase were evaluated by the modified Williamson-Hall plot. The results show that as higher is the increase in microstrain by thermal and training procedures, higher is the two-way memory strain of the NiTi sample. The micromechanical results pointed out that there is a certain formation of retained martensite during two-way memory training, but is not the main cause of the two-way shape memory effect. What is more, it seems that an early formation of retained martensite during training may decrease the generation of two-way shape memory effect. Pre-training thermal procedures that minimize the formation of retained martensite and maximize the increase in microstrain are fundamental to improve the generation of the NiTi two-way memory strain by subsequent training. [ABSTRACT FROM AUTHOR] |
| Copyright of Journal of Alloys & Compounds is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
| FullText | Text: Availability: 0 |
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| Header | DbId: egs DbLabel: Engineering Source An: 122840700 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Quantitative analysis of the microstructure in NiTi wires by Synchrotron X-ray diffraction: An approach to the cause of the Two Way Shape Memory Effect. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Urbina%2C+C%2E%22">Urbina, C.</searchLink><relatesTo>1</relatesTo><i> cristina.urbina@urv.cat</i><br /><searchLink fieldCode="AR" term="%22Gispert-Guirado%2C+F%2E%22">Gispert-Guirado, F.</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Ferrando%2C+F%2E%22">Ferrando, F.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22De+la+Flor%2C+S%2E%22">De la Flor, S.</searchLink><relatesTo>1</relatesTo> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Journal+of+Alloys+%26+Compounds%22">Journal of Alloys & Compounds</searchLink>. Jul2017, Vol. 712, p833-847. 15p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Shape+memory+alloys%22">Shape memory alloys</searchLink><br /><searchLink fieldCode="DE" term="%22Nickel-titanium+alloys%22">Nickel-titanium alloys</searchLink><br /><searchLink fieldCode="DE" term="%22Microstructure%22">Microstructure</searchLink><br /><searchLink fieldCode="DE" term="%22Wire%22">Wire</searchLink><br /><searchLink fieldCode="DE" term="%22X-ray+diffraction%22">X-ray diffraction</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: To understand the complex behaviour of the NiTi shape memory alloys, the use of advanced characterization techniques as Synchrotron X-ray diffraction, becomes more and more necessary. In this paper, this technique was performed in heat-treated, thermally cycled at zero stress and two-way memory trained NiTi wires to evaluate through microstrain and retained martensite which is the predominant micro-mechanism that cause the Two Way Shape Memory Effect. The microstructural effects in the structure of the Austenite by thermal and training methods were quantified separately for each NiTi sample, allowing us to calculate how much of the accumulated microstrain in the Austenite phase is due to the increment in density of dislocations and how much is consequence of the decrease in crystallite size. To achieve this, two different methodologies were used. The mean microstrain and shift index were calculated by analysing the whole diffractogram with the Rietveld method and the Double-Voigt Approach. The individual peak shift and the peak broadening of the Austenite phase were evaluated by the modified Williamson-Hall plot. The results show that as higher is the increase in microstrain by thermal and training procedures, higher is the two-way memory strain of the NiTi sample. The micromechanical results pointed out that there is a certain formation of retained martensite during two-way memory training, but is not the main cause of the two-way shape memory effect. What is more, it seems that an early formation of retained martensite during training may decrease the generation of two-way shape memory effect. Pre-training thermal procedures that minimize the formation of retained martensite and maximize the increase in microstrain are fundamental to improve the generation of the NiTi two-way memory strain by subsequent training. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Journal of Alloys & Compounds is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1016/j.jallcom.2017.04.071 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 15 StartPage: 833 Subjects: – SubjectFull: Shape memory alloys Type: general – SubjectFull: Nickel-titanium alloys Type: general – SubjectFull: Microstructure Type: general – SubjectFull: Wire Type: general – SubjectFull: X-ray diffraction Type: general Titles: – TitleFull: Quantitative analysis of the microstructure in NiTi wires by Synchrotron X-ray diffraction: An approach to the cause of the Two Way Shape Memory Effect. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Urbina, C. – PersonEntity: Name: NameFull: Gispert-Guirado, F. – PersonEntity: Name: NameFull: Ferrando, F. – PersonEntity: Name: NameFull: De la Flor, S. IsPartOfRelationships: – BibEntity: Dates: – D: 25 M: 07 Text: Jul2017 Type: published Y: 2017 Identifiers: – Type: issn-print Value: 09258388 Numbering: – Type: volume Value: 712 Titles: – TitleFull: Journal of Alloys & Compounds Type: main |
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