Early Stages of Precipitation in γ' Phase of a Ni–Al–Ti Model Alloy: Phase-Field and First-Principles Study

The early stages of precipitation process of the γ' phase of a Ni–Al–Ti alloy are investigated by microscopic phase-field and first-principles calculations. The simulated results indicate that a pre-precipitate with L10 structure appears before the L12 ordered phase, and then this metastable phase gradually transforms to L12 ordered phase; finally, the precipitated phase is composed of γ' ordered phase and γ matrix phase. The occupation probabilities of Al, Ni, and Ti atoms also illustrate the formation of the L10 phase and its situ conversion to L12 ordered phase constituted by a complicated compound Ni3(AlTi). Through the analyses of order parameter and occupation probability, the precipitation mechanism of γ' phase is drawn as a combination of congruent ordering and destabilization decomposition. Meanwhile, we also find that the growth and coarsening of the γ' phase occur via mixed mechanisms of Ostwald ripening and coalescence coarsening of neighboring precipitates. Moreover, the first-principles method is applied to calculate the thermodynamic parameters and validate further the appearance of the metastable phase and the site preference of Ti atom, which offers an explanation for atomic occupancy characteristics in the precipitate.

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Site preference of alloying elements in DO22-Ni3V phase: Phase-field and first-principles study

Metals and Materials International ◽

10.1007/s12540-015-5027-0 ◽

2015 ◽

Vol 21 (4) ◽

pp. 623-627 ◽

Cited By ~ 2

Author(s):

Ding-Ni Zhang ◽

Qian-Qian Shangguan ◽

Fu Liu ◽

Ming-Yi Zhang

Keyword(s):

Phase Field ◽

First Principles ◽

Alloying Elements ◽

Site Preference ◽

First Principles Study ◽

Phase Phase

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Computer Simulation of the Early Stage of Precipitation of L12-Ni3(Al,V) Using Microscopic Phase Field Method

Materials Science Forum ◽

10.4028/www.scientific.net/msf.817.809 ◽

2015 ◽

Vol 817 ◽

pp. 809-815

Author(s):

Wei Ping Dong ◽

Zheng Chen

Keyword(s):

Spinodal Decomposition ◽

Phase Field ◽

Early Stage ◽

Equilibrium Phase ◽

Field Method ◽

Phase Field Method ◽

Precipitation Process ◽

Interatomic Potentials ◽

Precipitation Mechanism ◽

Precipitation Phase

Based on the phase field theory, the long-range order (LRO) parameter related interatomic potentials equations were utilized to calculate the interatomic potentials of L10-Ni3(Al,V), L12-Ni3Al and L12-Ni3(Al,V) phases varying with temperature and concentrations. Using these potentials, the simulated microstructure evolution and the order parameter with the time of Ni75Al20V5 ternary alloy are simulated at temperature 1000K during the early stage of the precipitation process in this research. Results testify that the precipitation sequence during the early stage of Ni75Al20V5 alloy is the disordered phase →L10 pre-precipitation phase →L12 equilibrium phase. Firstly, the nonstoichiometric L10 pre-precipitation phase formed by congruent ordering precipitation mechanism; secondly, the nonstoichiometric L12 phase formed by transforming from L10 phase; thirdly, the stoichiometric equilibrium L12 phase formed by spinodal decomposition precipitation mechanism. It is discovered that the precipitation mechanism (congruent ordering+ spinodal decomposition) process was closely related to free energy and interatomic potentials: L10 pre-precipitation phase’s free energies are higher and interatomic potentials are smaller than those of L12 equilibrium phase.

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Site preference and atomic ordering in the ternary Rh5Ga2As: first-principles calculations

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1515/zkri-2021-2019 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Nilanjan Roy ◽

Sucharita Giri ◽

Harshit ◽

Partha P. Jana

Keyword(s):

Total Energy ◽

First Principles ◽

Density Functional ◽

Structure Type ◽

Site Preference ◽

X Ray Diffraction ◽

Atomic Ordering ◽

Functional Theory ◽

The Stability ◽

Bonding Characteristics

Abstract The site preference and atomic ordering of the ternary Rh5Ga2As have been investigated using first-principles density functional theory (DFT). An interesting atomic ordering of two neighboring elements Ga and As reported in the structure of Rh5Ga2As by X-ray diffraction data only is confirmed by first-principles total-energy calculations. The previously reported experimental model with Ga/As ordering is indeed the most stable in the structure of Rh5Ga2As. The calculation detected that there is an obvious trend concerning the influence of the heteroatomic Rh–Ga/As contacts on the calculated total energy. Interestingly, the orderly distribution of As and Ga that is found in the binary GaAs (Zinc-blende structure type), retained to ternary Rh5Ga2As. The density of states (DOS) and Crystal Orbital Hamiltonian Population (COHP) are calculated to enlighten the stability and bonding characteristics in the structure of Rh5Ga2As. The bonding analysis also confirms that Rh–Ga/As short contacts are the major driving force towards the overall stability of the compound.

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Electrocaloric effect in ferroelectric materials: from phase field to first-principles based effective Hamiltonian modeling

Materials Reports: Energy ◽

10.1016/j.matre.2021.100050 ◽

2021 ◽

pp. 100050

Author(s):

Jingtong Zhang ◽

Xu Hou ◽

Yajun Zhang ◽

Gang Tang ◽

Jie Wang

Keyword(s):

Phase Field ◽

First Principles ◽

Ferroelectric Materials ◽

Effective Hamiltonian ◽

Electrocaloric Effect

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Site preference of Y and Mn in nonstoichiometric BaTiO3 from first principles

Physical Review Materials ◽

10.1103/physrevmaterials.4.084601 ◽

2020 ◽

Vol 4 (8) ◽

Author(s):

Preston C. Bowes ◽

Jonathon N. Baker ◽

Douglas L. Irving

Keyword(s):

First Principles ◽

Site Preference

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Phase-field model of precipitation processes with coherency loss

npj Computational Materials ◽

10.1038/s41524-021-00503-x ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Tian-Le Cheng ◽

You-Hai Wen

Keyword(s):

Phase Field ◽

Field Model ◽

Ostwald Ripening ◽

Phase Field Model ◽

Energy Criterion ◽

Field Variable ◽

Ginzburg Landau ◽

Underlying Mechanisms ◽

Flood Fill ◽

Coherency Loss

AbstractA phase-field model is proposed to simulate coherency loss coupled with microstructure evolution. A special field variable is employed to describe the degree of coherency loss of each particle and its evolution is governed by a Ginzburg-Landau type kinetic equation. For the sake of computational efficiency, a flood-fill algorithm is introduced that can drastically reduce the required number of field variables, which allows the model to efficiently simulate a large number of particles sufficient for characterizing their statistical features during Ostwald ripening. The model can incorporate size dependence of coherency loss, metastability of coherent particles, and effectively incorporate the underlying mechanisms of coherency loss by introducing a so-called differential energy criterion. The model is applied to simulate coarsening of Al3Sc precipitates in aluminum alloy and comprehensively compared with experiments. Our results clearly show how the particle size distribution is changed during coherency loss and affects the coarsening rate.

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