Obaied A, Roslyakova I, To Baben M
ICAMS, Ruhr-University Bochum, Universitaetstr. 150, 44801, Bochum, Germany.
GTT-Technologies, Herzogenrath, Germany.
Sci Rep. 2022 Aug 4;12(1):13385. doi: 10.1038/s41598-022-16926-5.
A physically sound thermochemical model accounting for explicit thermal vacancies in elements and alloys is presented. The model transfers the latest theoretical understanding of vacancy formation into the Calphad formalism where it can extend currently available thermodynamic databases to cover vacancy concentrations without a complete re-assessment. The parametrization of the model is based on ab initio-calculated enthalpy of vacancy formation and two model parameters describing the excess heat capacity of vacancy formation. Excellent agreement is obtained with temperature-dependent vacancy concentrations and elemental heat capacities while reasonable extrapolation of phase stability to high temperatures is ensured. Extrapolation to multicomponent systems is reasonable and the long-standing Neumann-Kopp related problem in the Calphad community is solved since multicomponent solid solutions will no longer show fingerprints of elemental heat capacity peaks at their melting points. FCC-Ag, FCC-Al and FCC-Cu, FCC-Zn, FCC-Ni, BCC-Ti, and BCC-W are used as a demonstration, along with the Cu-Zn binary system.
提出了一个考虑元素和合金中显热空位的物理合理的热化学模型。该模型将对空位形成的最新理论理解转化为相图计算（Calphad）形式体系，在此体系中，它可以扩展当前可用的热力学数据库，以涵盖空位浓度，而无需进行全面重新评估。该模型的参数化基于从头算计算的空位形成焓以及描述空位形成过剩热容量的两个模型参数。与温度相关的空位浓度和元素热容量取得了极佳的一致性，同时确保了将相稳定性合理外推到高温。向多组分系统的外推是合理的，并且解决了相图计算领域长期存在的与诺伊曼-科普相关的问题，因为多组分固溶体在熔点时将不再显示元素热容量峰值的特征。以面心立方结构的银（FCC-Ag）、面心立方结构的铝（FCC-Al）、面心立方结构的铜（FCC-Cu）、面心立方结构的锌（FCC-Zn）、面心立方结构的镍（FCC-Ni）、体心立方结构的钛（BCC-Ti）和体心立方结构的钨（BCC-W）为例进行说明，同时还包括铜锌二元体系。
