权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Ab initio based calculation of the stability of selected TCP precipitates in steels: Temperature and interface effects

基于从头计算钢中选定 TCP 析出物稳定性的计算：温度和界面效应

基本信息

批准号：
289654611
负责人：
Privatdozent Dr. Thomas Hammerschmidt
金额：
--
依托单位：
Fachbereich 6.4: Materialinformatik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/289654611?language=en
关键词：
Ab initio based calculation stability

项目摘要

The mechanical properties and long-term stability of materials for high-temperature energy and transportation applications are strongly influenced by the precipitation of secondary phases. In particular, topologically closed-packed (TCP) precipitates play a decisive role in many technologically relevant alloys like the Fe-Nb system. While these phases are often clearly identified in experiments, their simulation is either limited to empirical models or to the stability of separate phases at T=0K. Therefore, a reliable prediction under which circumstances the precipitate phases form in the material is often not possible. Within the present project, we will apply ab initio based simulation techniques in order to understand, calculate and optimise the thermodynamic and microstructural conditions for the formation of complex precipitate phases. On the one hand, all entropy contributions for the free energy of formation up to the melting point will be determined with high accuracy. On the other hand the interfaces and the correlation of precipitates and microstructure of the matrix material will be considered. In contrast to previous approaches, the interplay of these two aspects will be mapped realistically in the simulation of precipitate formation.The concept of the project requires the use of a hierarchy of methods, which is achieved in a joint effort of two groups at the MPIE Düsseldorf and ICAMS Bochum. Density functional theory is needed for the accurate consideration of excitation processes at finite temperatures, whereas the microstructural description is achieved by a coarsening of the electronic structure towards a simplified description. The application of bond-order potentials makes the simulation of the combined microstructure of precipitate and matrix material accessible. The investigations of the present project will be focussed on the formation of Laves phases within the Fe-Nb system. This material system has a high potential for applications, is experimentally well characterized, but suffers from a limited understanding of precipitate formation. With the help of the project the competition between different TCP phases, the impact of further alloying elements on their stability, the expected morphology of the precipitates and the role of grain boundaries will be clarified. In addition to the direct interpretation of recent experimental measurements for Laves phases in Fe-Nb, the investigations will form the ground to an understanding of TCP precipitates in various material systems.

高温能源和运输应用材料的机械性能和长期稳定性受到二次相沉淀的强烈影响。特别是，拓扑密堆积 (TCP) 沉淀物在许多技术相关合金（如 Fe-Nb 系统）中发挥着决定性作用。虽然这些相通常在实验中被清楚地识别出来，但它们的模拟要么仅限于经验模型，要么仅限于 T=0K 时单独相的稳定性。因此，通常不可能可靠地预测在材料中形成沉淀相的情况。在本项目中，我们将应用基于从头算的模拟技术来理解、计算和优化复杂沉淀相形成的热力学和微观结构条件。一方面，直到熔点为止的形成自由能的所有熵贡献都将以高精度确定。另一方面，将考虑基体材料的界面以及析出物和微观结构的相关性。与以前的方法相比，这两个方面的相互作用将在沉淀物形成的模拟中得到真实的映射。该项目的概念需要使用层次结构的方法，这是通过 MPIE 杜塞尔多夫和 ICAMS 波鸿的两个团队的共同努力实现的。需要密度泛函理论来准确考虑有限温度下的激发过程，而微观结构描述是通过将电子结构粗化到简化描述来实现的。键序势的应用使得可以模拟沉淀物和基体材料的组合微观结构。本项目的研究将集中于 Fe-Nb 系统内 Laves 相的形成。该材料系统具有很高的应用潜力，经过实验很好地表征，但对沉淀物形成的了解有限。借助该项目，不同 TCP 相之间的竞争、其他合金元素对其稳定性的影响、析出物的预期形态以及晶界的作用将得到阐明。除了直接解释最近 Fe-Nb 中拉夫斯相的实验测量之外，这些研究还将为理解各种材料系统中的 TCP 沉淀物奠定基础。