Study on Ni-Ti alloys around equiatomic composition by the first-principles phase field method

Ohno, Kaoru; Tsuchiya, M.; Kuwahara, Riichi; Sahara, Ryoji; Bhattacharyya, Swastibrata; Pham, Thi Nu

doi:10.1016/j.commatsci.2021.110284

Cited by 8 publications

(6 citation statements)

References 15 publications

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“…In Figure 4c, an interdiffusion layer was observed at Ti/Ni interface. According to Ti–Ni binary phase diagram and the first principle method, [ 31 ] the possible intermetallic compounds at Ti/Ni interface are TiNi 3 , TiNi, and Ti 2 Ni in sequence. The existence of the interdiffusion layer indicates that metallurgical bonding occurs at the interface.…”

Section: Resultsmentioning

confidence: 99%

Failure Process Observation and Failure Mechanism of Ni‐Coated TC4 Alloy by Gradually Changed Curvature Bending Method

et al. 2021

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To observe the failure process of coating/substrate materials, a gradually changed curvature bending (GCCB) method is proposed, and the relevant equipment is developed. Before GCCB experiment, Ni-coated Ti6Al4V (TC4) samples were prepared. The effect of vacuum heat treatment on the microstructure at Ti/Ni interface is discussed. With the increase in heat treatment time, intermetallic compounds of TiNi 3 , TiNi, and Ti 2 Ni start to form. Kirkendall void forms in Ni coating at first, and then the pore number decreases due to interdiffusion. Based on the interdiffusion of Ni into TC4 substrate, β-Ti phase forms at the surface region. The whole failure process of Ni-coated TC4 sample by GCCB experiment is observed and analyzed. With the increase in bending curvature, the fracture order of each layer is TiNi 3 > Ti 2 Ni > TiNi. With the increase in heat treatment time, the bonding property of the coating first increases and then decreases, and the failure mode also changes. The failure occurs at TiNi 3 layer when the heat treatment time is 60 min. When the heat treatment time is 120 min, the bonding property of the coating is the highest and surface vertical crack occurs. When treated 180 min, failure occurs at Ti 2 Ni layer.

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Section: Resultsmentioning

confidence: 99%

Failure Process Observation and Failure Mechanism of Ni‐Coated TC4 Alloy by Gradually Changed Curvature Bending Method

et al. 2021

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“…As well as the total energy, the resulting local free energy becomes a stepwise function of the concentration, i.e., the number of atoms of each element inside one tetrahedron. The renormalization procedure is the same as our previous papers on the FPPF method, [10][11][12][13][14] which can be done automatically by using the Pipeline Pilot protocol. 11) Denoting the concentration, the chemical potential, the mobility, and the random force, respectively, as ϕ X , μ X , M X , and η for element X, we derive the Cahn-Hilliard equation from ∂ϕ…”

Section: Methodsmentioning

confidence: 99%

“…In the present paper, we apply two first-principles methods to the iron-rich region of the bcc FeSi alloy to clarify the origin of the zero magnetostriction and low magnetic anisotropy of Fe-6.5 wt% Si. One is the first-principles phase field (FPPF) method [10][11][12][13][14] and the other is the special quasirandom structure (SQS) method. [15][16][17] Both of them have distinct ability of predicting the free energy and microstructure of alloys without relying on any experimental or empirical information.…”

Section: Introductionmentioning

confidence: 99%

Microstructures in Iron-rich FeSi Alloys by First-principles Phase Field and Special Quasirandom Structure Methods

et al. 2023

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Coarse grained phase morphologies of iron-rich region of FeSi alloys at 1 050 K are investigated by using first-principles phase field and special quasirandom structure methods without relying on any experimental or empirical information. From the free energy comparison, we find that, for the Si concentration less than 25 at%, a solid-solution-like homogeneous phase is most stable, although a random pattern in nm scale consisting of B2 Fe 4-x Si x and D0 3 Fe 3 Si phases may appear at 12.5 at% Si at somewhat lower temperatures. We make a conjecture that, around 12.5 at% Si, such a random pattern in nm scale is the origin of the zero magnetostriction and low magnetic anisotropy. This solves a long-standing problem of the experimentally observed zero magnetostriction at 6.5 wt% Si. On the other hand, for the Si concentration slightly larger than 25 at%, FeSi alloys prefer two-phase coexistence of the D0 3 Fe 3 Si phase and the B2 FeSi phase. All these findings are in good accordance with the available experimental evidence.

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“…Another effective solution may involve a combination of the phase-field method with first-principles calculations (i.e., the first-principles phasefield (FPPF) method). [115][116][117][118] This would be desirable since it is not necessary to couple the FPPF method with the CALPHAD method because the first-principles free-energy calculations are performed simultaneously with the phasefield simulations. Furthermore, because the FPPF method does not require empirical parameters, it clearly represents one of the next-generation phase-field methods, and so in the future, FPPF models are expected to be applied to solidstate phase transformations in steel.…”

Section: Parameter Identificationmentioning

confidence: 99%

Phase-field Modeling and Simulation of Solid-state Phase Transformations in Steels

Yamanaka

2023

ISIJ Int.

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Study on Ni-Ti alloys around equiatomic composition by the first-principles phase field method

Cited by 8 publications

References 15 publications

Failure Process Observation and Failure Mechanism of Ni‐Coated TC4 Alloy by Gradually Changed Curvature Bending Method

Failure Process Observation and Failure Mechanism of Ni‐Coated TC4 Alloy by Gradually Changed Curvature Bending Method

Microstructures in Iron-rich FeSi Alloys by First-principles Phase Field and Special Quasirandom Structure Methods

Phase-field Modeling and Simulation of Solid-state Phase Transformations in Steels

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