Geometry and energy barrier of martensite in the initial stage martensitic transformation in B19’ TiNi shape memory alloy

Teramoto, Tadahisa; Nagahira, K.; Tanaka, Katsushi

doi:10.1016/j.actamat.2020.09.060

Cited by 11 publications

(3 citation statements)

References 41 publications

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“…This means that only one of the geometrically possible variant pairing appears in the actual phase transformation for the butterfly-pairing. This trend is reported also in shape memory alloys and explained by the elastic strain energy associated with pairing 30,31) .…”

Section: Comparison With Rank-1 Connection At the Junction Planesupporting

confidence: 66%

Geometry of Butterfly Martensite in Fe-18Ni-0.7Cr-0.5C Alloy

Takahashi,

Shinozaki,

Shinohara

et al. 2024

ISIJ Int.

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To clarify the geometry of the junction of martensite which forming butterfly-type martensite, electron microscopy, theoretical analysis using the phenomenological theory of martensite crystallography and rank-1 connection were carried out on Fe-18Ni-0.7Cr-0.5C (mass %) alloy.Martensite plates in this alloy exhibit {252} 𝛾 habit plane and K-S OR and are in good agreement with the double shear PTMC by Ross and Crocker. The frequency of formation of V1/V2 and V1/V16 (butterflies) pairs was 20% each, with these two pairs alone accounting for 40% of the total. Theoretical analysis using rank-1 connection of variants revealed that butterfly-pairing is not a geometrically compatible morphology, even for alloys in which butterfly martensite forms frequently. We have also revealed theoretically that the junction plane of the butterfly-pairing keeps (100) 𝛾 independent of the mode of lattice invariant shear (i.e. morphology of martensite plate). Preferential formation mechanism for butterfly-pairing is discussed based on the common lattice invariant deformation between V1 and V16.

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Section: Comparison With Rank-1 Connection At the Junction Planesupporting

confidence: 66%

Geometry of Butterfly Martensite in Fe-18Ni-0.7Cr-0.5C Alloy

Takahashi,

Shinozaki,

Shinohara

et al. 2024

ISIJ Int.

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“…Figures 3(d) – 3(f) (movie S1 ) show that the transformation process takes place within five seconds, and the geometry of the particles remains unchanged before this. This may be due to the energy barrier because it was reported that the transformation of the material structure needs to overcome a certain energy barrier [ 31 , 32 ]. With increasing time, when the accumulated energy exceeds the energy barrier needed for the structural transition, the reaction starts rapidly.…”

Section: Resultsmentioning

confidence: 99%

In Situ Investigation of the Phase Transition at the Surface of Thermoelectric PbTe with van der Waals Control

Cheng

Wang

et al. 2022

Research

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The structure of thermoelectric materials largely determines the thermoelectric characteristics. Hence, a better understanding of the details of the structural transformation process/conditions can open doors for new applications. In this study, the structural transformation of PbTe (a typical thermoelectric material) is studied at the atomic scale, and both nucleation and growth are analyzed. We found that the phase transition mainly occurs at the surface of the material, and it is mainly determined by the surface energy and the degree of freedom the atoms have. After exposure to an electron beam and high temperature, high-density crystal-nuclei appear on the surface, which continue to grow into large particles. The particle formation is consistent with the known oriented-attachment growth mode. In addition, the geometric structure changes during the transformation process. The growth of nanoparticles is largely determined by the van der Waals force, due to which adjacent particles gradually move closer. During this movement, as the relative position of the particles changes, the direction of the interaction force changes too, which causes the particles to rotate by a certain angle.

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“…While no twins were observed for the (111)-terminated

are playing a crucial role similar to the common thermal expansion [ 55 ]. Since twins with {111} habit planes have relatively small energy barriers compared to the other twins in TiNi [ 56 ] their formation is preferable. And in the case of a thin plate with (111)-termination can lead to the situation where the whole plate with a small thickness acts as a single twin.…”

Section: Resultsmentioning

confidence: 99%

Phase Transformation in TiNi Nano-Wafers for Nanomechanical Devices with Shape Memory Effect

et al. 2022

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Recently, Ti-Ni based intermetallic alloys with shape memory effect (SME) have attracted much attention as promising functional materials for the development of record small nanomechanical tools, such as nanotweezers, for 3D manipulation of the real nano-objects. The problem of the fundamental restrictions on the minimal size of the nanomechanical device with SME for manipulation is connected with size effects which are observed in small samples of Ti-Ni based intermetallic alloys with thermoplastic structural phase transition from austenitic high symmetrical phase to low symmetrical martensitic phase. In the present work, by combining density functional theory and molecular dynamics modelling, austenite has been shown to be more stable than martensite in nanometer-sized TiNi wafers. In this case, the temperature of the martensitic transition asymptotically decreases with a decrease in the plate thickness h, and the complete suppression of the phase transition occurs for a plate with a thickness of 2 nm, which is in qualitative agreement with the experimental data. Moreover, the theoretical values obtained indicate the potential for even greater minimization of nanomechanical devices based on SME in TiNi.

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Geometry and energy barrier of martensite in the initial stage martensitic transformation in B19’ TiNi shape memory alloy

Cited by 11 publications

References 41 publications

Geometry of Butterfly Martensite in Fe-18Ni-0.7Cr-0.5C Alloy

Geometry of Butterfly Martensite in Fe-18Ni-0.7Cr-0.5C Alloy

In Situ Investigation of the Phase Transition at the Surface of Thermoelectric PbTe with van der Waals Control

Phase Transformation in TiNi Nano-Wafers for Nanomechanical Devices with Shape Memory Effect

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