Distinguishing interstitial and substitutional diffusion in grand-potential based phase-field model
Distinguishing interstitial and substitutional diffusion in grand-potential based phase-field model
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DOI：
10.1016/j.mtla.2020.100820
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发表时间：
2020-08-01
期刊：
影响因子：
3.4
通讯作者：
Nestler, Britta
中科院分区：
文献类型：
--
作者：
Amos, P. G. Kubendran;Nestler, Britta
基于大势的相场技术通常被认为是多组分系统相变建模的有效方法。由于该技术主要采用摩尔分数来处理浓度，因此主要局限于模拟完全由取代扩散控制的微观结构演变。在这项工作中，现有的大势模型被重新制定，以涵盖间隙扩散。通过采用基于摩尔数-密度（mol/m(3)）的成分描述来区分间隙扩散和取代扩散。通过模拟Fe-C-Mn三元体系中奥氏体向铁素体的直接分解，阐明了重新表述的方法模拟伴随间隙扩散和取代扩散的相变的能力。能量密度近似有助于将CALPHAD数据合并到本框架中，为一般，特别是为Fe-C-X合金系统描述。此外，本文还模拟了准平衡状态下的相变，这种相变只能通过重新制定的大势技术来实现，并讨论了由此产生的浓度分布，与传统方法的结果进行了比较。在约束碳平衡条件下，碳的分配与描述一致。
Grand-potential based phase-field technique is often claimed to be an efficient approach for modelling phase transformation in multicomponent systems. Since this technique largely employs mole fraction to treat concentration, it is principally restricted to simulating microstructural evolutions which are exclusively governed by substitutional diffusion. In this work, an existing grand-potential model is re-formulated to encompass interstitial diffusion. The distinction between interstitial and substitutional diffusion is achieved by adopting molar number-density (mol/m(3)) based description of composition. The ability of the re-formulated approach to model phase transformation accompanying interstitial and substitutional diffusion is elucidated by simulating rather straightforward decomposition of austenite into ferrite in the ternary Fe-C-Mn system. Energy-density approximations that facilitate the incorporation of CALPHAD data in the present framework are delineated for general, and in particular for Fe-C-X alloy systems. Furthermore, phase-change under para-equilibrium, which can only be imposed through the re-formulated variant of grand-potential technique, is modelled and the resulting concentration profile is discussed in comparison to the outcomes of the conventional approach. Partitioning of carbon in constrained-carbon-equilibrium condition is consistently simulated in-line with its description.