First principles calculation of composition dependence tracer and interdiffusion with phase change in γ/γ′ superalloy: A case study of Ir/Ir3Nb

IF 1.9 3区材料科学 Q4 CHEMISTRY, PHYSICAL

Calphad-computer Coupling of Phase Diagrams and Thermochemistry Pub Date : 2024-01-17 DOI:10.1016/j.calphad.2024.102659

Haiyu Luo , Wensheng Liu , Haoran Gong , Chaoping Liang

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Abstract

In this work, the composition dependent tracer and interdiffusion coefficient with phase change in γ/γ′ Ir/Ir₃Nb superalloy are studied by means of first-principles calculation together with nudged elastic band, and quasi−harmonic thermodynamics. The formulae scattered in the literature for composition dependence tracer diffusion coefficient are summarized and executed using first principles calculation. Each term in the newly derived formulae, such as energy barrier, jump frequency, defect concentration, correlation, solvent enhancement factor, effective escape frequency, etc. is meticulously calculated. We find the composition dependent tracer diffusion coefficient of Nb in L1₂ γ′-Ir₃Nb phase is contributed mainly from the antisite bridge rather than five-frequency model proposed in FCC γ-Ir dilute solid solution. The faster diffuser is Nb in γ-Ir, while Ir in γ′-Ir₃Nb. Based on the tracer diffusion coefficient, the interdiffusion coefficient is obtained using Darken-Manning equation. The composition profile and phase boundary movement of γ/γ′ Ir/Ir₃Nb superalloy are evaluated through an analytical solution of Matano-Boltzmann equations. The calculated diffusion coefficients and composition profile are in good agreement with experiments. Our findings not only serve as a successful example for the quantitative calculation of composition dependent tracer diffusion coefficient, but also shed lights on the physics behind the diffusion in intermetallics.

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γ/γ′超合金中与成分相关的示踪和相变相互扩散的第一性原理计算：Ir/Ir3Nb 案例研究

本文通过第一性原理计算，结合裸弹带和准谐热力学，研究了γ/γ′ Ir/Ir3Nb 超合金中与成分相关的示踪剂扩散系数和相变时的相互扩散系数。利用第一性原理计算总结并执行了散见于文献中的成分依赖性示踪剂扩散系数公式。新推导公式中的每个项，如能障、跃迁频率、缺陷浓度、相关性、溶剂增强因子、有效逸出频率等，都经过了细致的计算。我们发现，L12 γ′-Ir3Nb相中铌的示踪扩散系数与成分有关，主要来自反斜桥，而非 FCC γ-Ir稀固溶体中提出的五频模型。γ-Ir中扩散较快的是Nb，而γ′-Ir3Nb中扩散较快的是Ir。根据示踪剂扩散系数，利用 Darken-Manning 方程求得相互扩散系数。通过马坦诺-玻尔兹曼方程的解析解，评估了 γ/γ′ Ir/Ir3Nb 超合金的成分剖面和相界运动。计算得出的扩散系数和成分曲线与实验结果十分吻合。我们的研究结果不仅是定量计算随成分变化的示踪剂扩散系数的成功范例，而且还揭示了金属间化合物扩散背后的物理学原理。

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来源期刊

Calphad-computer Coupling of Phase Diagrams and Thermochemistry 化学-热力学

CiteScore

4.00

自引率

16.70%

发文量

审稿时长

2.5 months

期刊介绍： The design of industrial processes requires reliable thermodynamic data. CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) aims to promote computational thermodynamics through development of models to represent thermodynamic properties for various phases which permit prediction of properties of multicomponent systems from those of binary and ternary subsystems, critical assessment of data and their incorporation into self-consistent databases, development of software to optimize and derive thermodynamic parameters and the development and use of databanks for calculations to improve understanding of various industrial and technological processes. This work is disseminated through the CALPHAD journal and its annual conference.