Low-Temperature Mechanical Instabilities Govern High-Temperature Thermodynamics in the Austenite Phase of Shape Memory Alloy Constituents: Ab Initio Simulations of NiTi, NiZr, NiHf, PdTi, and PtTi

Haskins, Justin B.; Malmir, Hessam; Honrao, Shreyas; Sandoval, Luis; Lawson, John W.

doi:10.1016/j.actamat.2021.116872

Cited by 27 publications

(13 citation statements)

References 79 publications

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“…Meanwhile, the atomistic simulation using the electronic structure calculation of density functional theory (DFT) found a more stable B33 phase (B19' is a metastable structure), which has a larger monoclinic angle than that of B19'. However, this has not been observed in experiments [5][6][7][8][9][10]. The reason for this discrepancy between the experimental and simulation results remains controversial.…”

Section: Introductionmentioning

confidence: 88%

“…Several previous studies have suggested that the reason for this is that the observed B19' phase is stabilized through internal stresses; however, a detailed analysis of the internal stresses is lacking [5,11]. Recently, Haskins et al [10] discussed the reason for the thermal stability of B19' and B33 using DFT-calculated free energy, E-mail address: ishii@me.es.osaka-u.ac.jp. which includes vibration entropy.…”

Section: Introductionmentioning

confidence: 99%

“…In this sense, even if the B33 phase nucleates heterogeneously in the B2 matrix, its monoclinic angle will be lower than that of DFTcalculated one. Because the atomic structure of the B19' phase can be considered as an affinely deformed structure of the B33 phase with small shuffling components of internal coordinates [8][9][10], from a micromechanical perspective, it can be explained as follows. The experimentally observed B19' structure is an elastically deformed B33 structure by the internal back stress by the B2 matrix, or the internal back stress by the B2 matrix totally changes it to the B19' phase.…”

Section: Introductionmentioning

confidence: 99%

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Elastic investigation for the existence of B33 phase in TiNi shape memory alloys using atomistically informed Eshelby’s ellipsoidal inclusion

Ishii

2023

Computational Materials Science

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Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Elastic investigation for the existence of B33 phase in TiNi shape memory alloys using atomistically informed Eshelby’s ellipsoidal inclusion

Ishii

2023

Computational Materials Science

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“…Although each LPEM is a stable structure, the barrier on the transformation path from a LPEM to the groundstate is very low (∼1 meV/atom, see Figure 4 in [5]). While the highly symmetric cubic B2 structure is unstable [8,43], one may use one of the stable representative structures for an approximate description of NiTi austenite [20].…”

Section: Niti Austenitementioning

confidence: 99%

Between Harmonic Crystal and Glass: Solids with Dimpled Potential-Energy Surfaces Having Multiple Local Energy Minima

Zarkevich

Johnson

2022

Crystals

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Solids with dimpled potential-energy surfaces are ubiquitous in nature and, typically, exhibit structural (elastic or phonon) instabilities. Dimpled potentials are not harmonic; thus, the conventional quasiharmonic approximation at finite temperatures fails to describe anharmonic vibrations in such solids. At sufficiently high temperatures, their crystal structure is stabilized by entropy; in this phase, a diffraction pattern of a periodic crystal is combined with vibrational properties of a phonon glass. As temperature is lowered, the solid undergoes a symmetry-breaking transition and transforms into a lower-symmetry phase with lower lattice entropy. Here, we identify specific features in the potential-energy surface that lead to such polymorphic behavior; we establish reliable estimates for the relative energies and temperatures associated with the anharmonic vibrations and the solid–solid symmetry-breaking phase transitions. We show that computational phonon methods can be applied to address anharmonic vibrations in a polymorphic solid at fixed temperature. To illustrate the ubiquity of this class of materials, we present a range of examples (elemental metals, a shape-memory alloy, and a layered charge-density-wave system); we show that our theoretical predictions compare well with known experimental data.

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“…For TiNi films the nonlinear declining character of the martensitic transformation temperature on their thickness is detected [ 32 ]. Along with experimental study, the computer simulations approaches have been applied to understand phase transitions at low-dimensional systems, specifically, the molecular dynamics (MD) method [ 33 , 34 ]. For example, according to Ref.…”

Section: Introductionmentioning

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.

show abstract

Low-Temperature Mechanical Instabilities Govern High-Temperature Thermodynamics in the Austenite Phase of Shape Memory Alloy Constituents: Ab Initio Simulations of NiTi, NiZr, NiHf, PdTi, and PtTi

Cited by 27 publications

References 79 publications

Elastic investigation for the existence of B33 phase in TiNi shape memory alloys using atomistically informed Eshelby’s ellipsoidal inclusion

Elastic investigation for the existence of B33 phase in TiNi shape memory alloys using atomistically informed Eshelby’s ellipsoidal inclusion

Between Harmonic Crystal and Glass: Solids with Dimpled Potential-Energy Surfaces Having Multiple Local Energy Minima

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

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