Darvishi Kamachali Reza
Federal Institute for Materials Research and Testing (BAM) Unter den Eichen 87 12205 Berlin Germany
Max-Planck-Institut für Eisenforschung Max-Planck-Str. 1 40237 Düsseldorf Germany.
RSC Adv. 2020 Jul 17;10(45):26728-26741. doi: 10.1039/d0ra04682e. eCollection 2020 Jul 15.
Systematic microstructure design requires reliable thermodynamic descriptions of each and all microstructure elements. While such descriptions are well established for most bulk phases, thermodynamic assessment of microstructure defects is challenging because of their individualistic nature. In this paper, a model is devised for assessing grain boundary thermodynamics based on available bulk thermodynamic data. We propose a continuous relative atomic density field and its spatial gradients to describe the grain boundary region with reference to the homogeneous bulk and derive the grain boundary Gibbs free energy functional. The grain boundary segregation isotherm and phase diagram are computed for a regular binary solid solution, and qualitatively benchmarked for the Pt-Au system. The relationships between the grain boundary's atomic density, excess free volume, and misorientation angle are discussed. Combining the current density-based model with available bulk thermodynamic databases enables constructing databases, phase diagrams, and segregation isotherms for grain boundaries, opening possibilities for studying and designing heterogeneous microstructures.
系统的微观结构设计需要对每个及所有微观结构元素进行可靠的热力学描述。虽然对于大多数体相而言，此类描述已相当成熟，但由于微观结构缺陷的个体化性质，对其进行热力学评估具有挑战性。本文基于现有的体相热力学数据，设计了一个用于评估晶界热力学的模型。我们提出了一个连续的相对原子密度场及其空间梯度，以参照均匀体相来描述晶界区域，并推导了晶界吉布斯自由能泛函。针对规则二元固溶体计算了晶界偏聚等温线和相图，并对Pt-Au体系进行了定性基准测试。讨论了晶界的原子密度、过量自由体积和取向差角之间的关系。将当前基于密度的模型与现有的体相热力学数据库相结合，能够构建晶界的数据库、相图和偏聚等温线，为研究和设计异质微观结构开辟了可能性。
