What EBSD and TKD Tell Us about the Crystallography of the Martensitic B2-B19′ Transformation in NiTi Shape Memory Alloys

Cayron, Cyril

doi:10.3390/cryst10070562

Cited by 23 publications

(21 citation statements)

References 81 publications

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“…ð Þ B19 0 as also previously observed for the conventionally fabricated NiTi alloys (Ref [39][40][41]. The analysis of the IPF maps revealed also the formation of extremely fine twins within the primary needles at higher deformation.…”

Section: In Situ Deformation Studiessupporting

confidence: 82%

Microstructure, Mechanical Properties, and Martensitic Transformation in NiTi Shape Memory Alloy Fabricated Using Electron Beam Additive Manufacturing Technique

Rogal

Kalita

Kawałko

et al. 2021

J. of Materi Eng and Perform

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The electron beam additive manufacturing (EBAM) method was applied in order to fabricate rectangular-shaped NiTi component. The process was performed using an electron beam welding system using wire feeder inside the vacuum chamber. NiTi wire containing 50.97 at.% Ni and showing martensitic transformation near room temperature was used. It allowed to obtain a good quality material consisting of columnar grains elongated into the built direction growing directly from the NiTi substrate, which is related to the epitaxial grain growth mechanism. As manufactured material showed martensitic and reverse transformations diffused over the temperature range from −10 to 44 °C, the applied aging at 500° C moved the transformation to higher temperatures and transformation peaks became sharper. The highest recoverable strain of about 3.5% was obtained in the as-deposited sample deformed along the deposition direction. In the case of deformation of the alloy aged at 500 °C for 2h, the formation of martensite occurs at significantly lower stress; however, at about 2.5% the stress begins to increase gradually and only a small shape recovery was observed due to a higher martensitic transformation temperature. In situ SEM tensile deformation in the direction perpendicular to deposition direction showed that the martensite began to appear at the surface of the sample and at the grain boundaries due to heterogeneous nucleation. In situ studies allowed to determine the following crystallographic relationships between B2 and B19’ martensite: (100)B2||(100)B19’ and (100) B2 || (011)B19’; (011)B2|| (001)B19’ and $${(011)}_{\mathrm{B}2}||{\left(11\bar{1 }\right)}_{\mathrm{B}1{9}^{\mathrm{^{\prime}}}}$$ ( 011 ) B 2 | | 11 1 ¯ B 1 9 ′ . Samples aged at 500 °C exhibited fully austenitic microstructure; however, with increasing degree of deformation, the formation of martensite was observed. The majority of needles were tilted about 45° with respect to the tensile direction, and the presence of type I (11 $$\bar{1 }$$ 1 ¯ ) invariant twin boundaries was observed at higher degrees of deformation.

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Section: In Situ Deformation Studiessupporting

confidence: 82%

Microstructure, Mechanical Properties, and Martensitic Transformation in NiTi Shape Memory Alloy Fabricated Using Electron Beam Additive Manufacturing Technique

Rogal

Kalita

Kawałko

et al. 2021

J. of Materi Eng and Perform

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“…The dominant OR between austenite and B19 martensite was noted: AQ; it is also the "natural" OR, i.e., that for which the dense planes and dense directions of austenite and martensite are parallel. The habit plane of the large martensitic laths predicted from the individual lattice distortion associated with the OR AQ is (112) B2 (101) B19 , which is in good agreement with literature (see Section 2) and with the EBSD maps [24]. The additional ORs were interpreted as "closing-gap" ORs required to maintain the compatibility between variants.…”

Section: Introductionsupporting

confidence: 86%

“…The simple use of the distortion matrix F without the complex machinery of PTMC was successful to understand the variant selection in AuCu red gold alloys [67,68]. The knowledge of distortion matrix F associated with the natural OR is also sufficient to predict the habit planes of martensite in NiTi alloys [24].…”

Section: The Hidden Algebraic Structure Of Variantsmentioning

confidence: 99%

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The Correspondence Theory and Its Application to NiTi Shape Memory Alloys

Cayron

2022

Crystals

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Martensite crystallography is usually described by the phenomenological theory of martensite crystallography (PTMC). This theory relies on stretch matrices and compatibility equations, but it does not give a global view on the structures of variants, and it masks the relative roles of the symmetries and metrics. Here, we propose an alternative theory called correspondence theory (CT) based on correspondences and symmetries. The compatibility twins between the martensite variants are inherited by correspondence from the symmetry elements of austenite. We show that, for the B2 to B19′ transformation, there is a one-to-one relation between the specific misorientations and the specific inter-correspondences between the variants. For each type of misorientation, the twin of its junction plane can be predicted without calculating the stretch matrices, as in PTMC. The rational elements of the twins do not depend on the metrics; all the transformation twins are thus “generic”. We also introduce the concept of a weak plane that permits to explain the junction planes for polar pairs of variants for which the PTMC compatibility equations cannot be solved. The predictions are validated by comparison with experimental Transmission Kikuchi Diffraction (TKD) maps.

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“…A number of works is devoted to structural transformations in alloys based on titanium nickelide [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. However, the published results regarding the structure and properties of these materials are contradictory.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Properties of Nickel-Titanium Alloy during Martensitic Transformations under Plastic and Elastic Deformation

et al. 2021

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This paper focuses on the processes of the occurrence of magnetization during structure formation in samples of Ni51Ti49 alloy under deformation conditions. The possibility of the existence of a phase with an FCC (face-centered cubic) lattice in titanium nickelide has been demonstrated by electron microscopy and electron diffraction. It has been discovered that the interplanar distances of BCC110 (body-centered cubic), FCC111, and HCP002 (hexagonal close packed) in the alloy under study have similar values, which indicates the possibility of their mutual polymorphic transformation. Based on the modular self-organization, a scheme of martensitic transformations in titanium nickelide from the B2 structure (BCC lattice) to the B19’ structure (HCP lattice) through an intermediate phase with an FCC lattice is proposed. It is shown that lenticular crystals appear in the Ni51Ti49 alloy under tensile deformation until rupture, which is accompanied by the onset of ferromagnetism. The effect of magnetization in Ni51Ti49 samples when immersed in liquid nitrogen has been also discovered. In this case, the reason for the appearance and disappearance of magnetization can be associated with microdeformation processes caused by direct and reverse martensitic transitions that occur during cooling and heating of the samples.

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What EBSD and TKD Tell Us about the Crystallography of the Martensitic B2-B19′ Transformation in NiTi Shape Memory Alloys

Cited by 23 publications

References 81 publications

Microstructure, Mechanical Properties, and Martensitic Transformation in NiTi Shape Memory Alloy Fabricated Using Electron Beam Additive Manufacturing Technique

Microstructure, Mechanical Properties, and Martensitic Transformation in NiTi Shape Memory Alloy Fabricated Using Electron Beam Additive Manufacturing Technique

The Correspondence Theory and Its Application to NiTi Shape Memory Alloys

Magnetic Properties of Nickel-Titanium Alloy during Martensitic Transformations under Plastic and Elastic Deformation

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