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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.

用于高温能源和运输应用的材料的机械性能和长期稳定性受到第二相沉淀的强烈影响。特别是，拓扑密堆积（TCP）沉淀物在许多技术相关的合金中起着决定性的作用，如Fe-Nb系统。虽然这些阶段通常在实验中明确识别，但它们的模拟要么局限于经验模型，要么局限于T= 0 K时分离相的稳定性。因此，通常不可能可靠地预测在何种情况下在材料中形成沉淀相。在本项目中，我们将应用基于从头计算的模拟技术，以理解，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，所有的熵贡献的自由能的形成，直到熔点将被确定具有高精度。另一方面，将考虑界面和基体材料的析出物和显微组织的相关性。与以前的方法相比，这两个方面的相互作用将在模拟沉淀物形成中真实地映射。该项目的概念需要使用一系列方法，这是在MPIE杜塞尔多夫和ICAMS波鸿的两个小组的共同努力下实现的。密度泛函理论是需要在有限的温度下的激发过程的准确考虑，而微观结构的描述是通过对一个简化的描述粗糙的电子结构实现的。键序势的应用使得模拟析出相和基体材料的结合组织变得容易。本项目的研究将集中在Fe-Nb系统中Laves相的形成上。这种材料系统具有很高的应用潜力，实验上很好地表征，但对沉淀物形成的理解有限。在该项目的帮助下，不同TCP相之间的竞争，进一步合金化元素对其稳定性的影响，沉淀物的预期形态和晶界的作用将得到澄清。除了直接解释最近的实验测量的Laves相在Fe-Nb，调查将形成地面TCP沉淀物在各种材料系统的理解。