Diffusion in High Entropy Alloys

采用新型示踪-扩散耦合技术研究了高熵合金（HEAs）中的扩散，并建立了基于对扩散概念的扩展示踪扩散数据库。在第一个资助阶段，重点是建立实验和理论技术以及一般数据库的开发，而拟议的扩展旨在系统地检查示踪-扩散偶联方法，该方法可以考虑实际多主元素合金中可能遇到的各种情况，包括完全混相，相形成，复杂的相互扩散路径和强烈的体积变化。同时，多组分HEAs中扩散的模型描述必须扩展，以考虑空位作为一个单独的物种，不同子晶格的出现顺序，间隙溶解原子的影响以及沿相互扩散路径的摩尔体积变化。实验分析和理论描述方法的阐述将以协调一致的方式进行，应用基于calphad型描述和已开发的成对扩散模型的组合实验建模分析。我们的研究的动机是迫切需要提供可靠的动力学数据库，以充分预测多主元素合金（包括HEAs和成分复杂合金（CCAs））中的扩散现象。此外，我们将开发一个原子迁移性的自动化评估软件，并与新的迁移性数据库相结合。在SPP 2006 CCA-HEA框架内与合作伙伴的密切和富有成效的互动将激励和支持我们的见解和方法转移到其他材料班级，特别是BCC HEAs和选定的cca。

Diffusion in High Entropy Alloys (HEAs) is investigated using novel tracer-interdiffusion couple technique and compiled in an extended tracer diffusion database based on the pair-diffusion concept. While in the first funding period the focus lay on the establishment of the experimental and theoretical techniques as well as the general data base development, the proposed extension aims to examine systematically the tracer-interdiffusion couple method accounting for various situations which may be met in real multi-principal element alloys, including full miscibility, phase formation, complex interdiffusion paths, and strong volumetric changes. Simultaneously, the model description of diffusion in multicomponent HEAs has to be extended to account for vacancies as a separate species, ordering with appearance of different sub-lattices, influence of interstitially dissolved atoms and molar volume change along the interdiffusion path. The elaboration of the methodologies of experimental analysis and theoretic description will be done in a concerted way applying a combined experiment-modelling ansatz based on the CALPHAD-type description and the developed pair-wise diffusion model.Our research is motivated by the urgent need to provide reliable kinetic databases for adequate prediction of diffusion phenomena in multi-principal element alloys including both HEAs and compositionally complex alloys (CCAs). Furthermore, we will develop an automated assessment software for atomic mobilities and combine with the novel mobility database.A close and fruitful interaction with partners in the framework of SPP 2006 CCA-HEA will motivate and support the transfer of our insights and methods to other material classes and in particular to BCC HEAs and selected CCAs.