Calphad coupled phase-field model with mechano-chemical contributions and its application to rafting of γ′ in CMSX-4
Calphad coupled phase-field model with mechano-chemical contributions and its application to rafting of γ′ in CMSX-4
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DOI：
10.1016/j.commatsci.2020.109909
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发表时间：
2020-11-01
影响因子：
3.3
通讯作者：
Zhou, B.
中科院分区：
文献类型：
--
作者：
Boettger, B.;Apel, M.;Zhou, B.
提出了一种新的Calphad耦合的机械力-化学相场模型，该模型除了对驱动力的化学弹性贡献外，还包括机械力-化学对扩散（应力驱动扩散）、平衡组成和驱动力的影响。这些效果有其起源的浓度依赖性的本征应变，并可以显着影响相变动力学，特别是在镍基高温合金中，不同的溶解元素具有强烈不同的偏摩尔体积。在本文中，所有的机械力化学的贡献，扩散，平衡浓度和驱动力来自从自由能泛函。为了将该模型与Calphad数据库结合使用，通过对化学准平衡数据的后验处理，有效地、一致地引入了弹性效应，并首次应用该模型计算了二元Ni-Al和三元Ni-Al-Mo合金中单个γ '粒子的三维平衡形状，进而模拟了多元合金CMSX-4的Ostwald熟化和筏化。从模拟结果与不考虑机械力化学的贡献进行了比较。结果表明，特别是在三元和多元合金中，机械力化学效应对γ ′-粒子的平衡形状和界面动力学的影响是不可忽视的。此外，不同的标准均匀化假设的应力和应变内的扩散界面区域（福格特-泰勒，Khachaturyan，Reuss-Sachs）进行了系统的比较和分析，使用扩展的准平衡方法，导致一个新的评估其适用性的背景下的机械力-化学耦合。
A novel Calphad coupled mechano-chemical phase-field model is presented which in addition to chemo-elastic contributions to the driving force further includes mechano-chemical effects on diffusion (stress-driven diffusion), equilibrium compositions and driving force. These effects have their origin in the concentration dependency of the eigenstrains and can significantly influence the phase transformation kinetics, especially in Ni-based superalloys where the different dissolved elements have strongly different partial molar volumes. In this paper, all mechano-chemical contributions to diffusion, equilibrium concentrations and driving force are derived starting from a free energy functional. In order to use the model in conjunction with Calphad databases, elastic effects are incorporated in an efficient and consistent way by a posteriori treatment of the chemical quasi-equilibrium data.The new model is first applied to evaluate the 3D-equilibrium shape of a single gamma'-particle in a binary Ni-Al and a ternary Ni-Al-Mo alloy and then for the simulation of Ostwald ripening and rafting of the multicomponent CMSX-4 alloy. Results from simulations with and without consideration of the mechano-chemical contributions are compared. It is shown that, especially in case of the ternary and multicomponent alloys, the mechano-chemical effects on the equilibrium shapes of the gamma'-particles and on interface kinetics are considerable and cannot be neglected. Moreover, different standard homogenization assumptions for stresses and strains inside the diffuse interface region (Voigt-Taylor, Khachaturyan, Reuss-Sachs) have been systematically compared and analyzed using an extended quasi-equilibrium approach, leading to a new evaluation of their applicability in the context of mechano-chemical coupling.