Diffusion in high entropy alloys: Development and application of an experiment-ab initio approach

高熵合金中的扩散：从头开始实验方法的开发和应用

• 批准号: 397350460
• 负责人: Professor Dr. Sergiy Divinski
• 金额: --
• 依托单位: Max-Planck-Institut für Eisenforschung GmbH (MPIE)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/397350460?language=en
• 关键词: Diffusion; entropy; alloys; Development; application

Reliable control over phase decomposition and creep behavior of high entropy alloys (HEAs) represents an enormous challenge in view of their multi-principal element nature and presumably slow diffusion. The present project DIFFINITIO aims at tackling this challenge from a fundamental perspective by developing and applying an integrated experiment-ab initio approach for the determination of accurate diffusion coefficients in HEAs. The proposal relies on the leading and unique expertise of the applicants in the fields of radiotracer diffusion measurements and finite temperature ab initio computations. With our investigations we will provide fundamental insights into the basic atomistic mechanisms of diffusion in HEAs, quantifying the impact of the multi-element environment, and scrutinizing postulated concepts as the one of sluggish diffusion.We focus on a specific, non-magnetic material system, the AlHfScTiZr HEA. AlHfScTiZr crystallizes on the hcp lattice and may develop sublattices ordering depending on the Al concentration. The temperature dependencies of the self-diffusion rates of all principal elements (with Zn as Al substitute) in the selected AlHfScTiZr HEA will experimentally be determined and evaluated from the DFT-based barrier calculations and the cluster expansion-based kinetic Monte carlo simulations enabling direct a direct quantification of the correlation and short-range ordering effects. The sublattice ordering is a fascinating feature because it affects strongly self-diffusion and solute diffusion rates. Preliminary investigations show clearly that small transition-metal elements like Ni are ultrafast interstitial diffusers in this alloy. Their diffusion rates are higher than those expected for self-diffusion by four orders of magnitude. This is counterintuitive and the mechanism behind the ultrafast diffusers is not clarified so far. As a part of the proposal, we suggest to develop a unique and extremely sensitive experimental tool for addressing the early stages of phase decomposition and formation and evolution of ordering, making use of the phenomenon of ultrafast diffusion. A significant advance in the basic understanding of fundamental HEA concepts is expected with the accomplishment of the DIFFINITIO project, especially in view of the present absence of reliable diffusion data for this material class in the literature.

鉴于高熵合金 (HEA) 的多主要元素性质和可能的缓慢扩散特性，对高熵合金 (HEA) 的相分解和蠕变行为进行可靠控制是一项巨大的挑战。目前的 DIFFINITIO 项目旨在通过开发和应用集成的从头开始实验方法来确定 HEA 中的精确扩散系数，从根本上应对这一挑战。该提案依赖于申请人在放射性示踪剂扩散测量和有限温度从头计算领域的领先和独特的专业知识。通过我们的研究，我们将对 HEA 中扩散的基本原子机制提供基本见解，量化多元素环境的影响，并仔细审查作为缓慢扩散概念的假设概念。我们专注于一种特定的非磁性材料系统，AlHfScTiZr HEA。 AlHfScTiZr 在 hcp 晶格上结晶，并可能根据 Al 浓度形成亚晶格排序。所选 AlHfScTiZr HEA 中所有主要元素（以 Zn 作为 Al 替代品）的自扩散速率的温度依赖性将通过基于 DFT 的势垒计算和基于团簇膨胀的动力学蒙特卡罗模拟进行实验确定和评估，从而能够直接进行相关性和短程排序效应的直接量化。 亚晶格排序是一个令人着迷的特征，因为它强烈影响自扩散和溶质扩散速率。初步研究清楚地表明，镍等小型过渡金属元素是该合金中的超快间隙扩散体。它们的扩散速率比预期的自扩散速率高四个数量级。这是违反直觉的，并且超快扩散器背后的机制迄今为止尚未阐明。作为该提案的一部分，我们建议开发一种独特且极其敏感的实验工具，利用超快扩散现象来解决相分解以及有序形成和演化的早期阶段。随着 DIFFINITIO 项目的完成，预计对基本 HEA 概念的基本理解将取得重大进展，特别是考虑到文献中目前缺乏此类材料的可靠扩散数据。