Structure-properties relations in single phase fcc and bcc high entropy alloys under a tribological load

摩擦载荷下单相面心立方和体心立方高熵合金的结构-性能关系

• 批准号: 409484397
• 负责人: Professor Dr. Christian Greiner
• 金额: --
• 依托单位: Institut für Angewandte Materialien - Werkstoffkunde (IAM-WK)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/409484397?language=en
• 关键词: Structure; properties; relations; single; phase

The study of interacting surfaces in relative motion - called tribology - is of great importance in modern life, particularly for metallic materials which are ubiquitously used in engineering components. From a materials scientist’s point of view, tribology is an extremely interesting field as phenomena like the evolution of the subsurface microstructure are only understood phenomenologically. This is especially true for high entropy alloys (HEAs), as a novel class of metallic alloys, which hold the promise of outstanding tribological properties. There is no comprehensive knowledge yet about the changes in the subsurface microstructure while sliding and the elementary mechanisms responsible for the microstructure’s evolution. Among the mechanisms that might be at work are dislocation slip, twinning, the development of shear bands, oxidation and mechanical mixing. This so far incomplete picture results in the lack of a structure-properties relation for HEAs in frictional contacts. Combining the complementary expertise of the Heilmaier group, focused on alloy development, and the Greiner group, with its track record in materials tribology, our research will tackle three central research questions: (A) Is there a defined correlation between the parameters of the initial microstructure of high entropy alloys and their friction and wear properties? (B) Are these elementary mechanisms correlated with fundamental deformation mechanisms obtained under uniaxial, monotonic load? (C) Can these properties and correlations be understood in light of characteristics unique to HEAs, like severe lattice distortion, sluggish diffusion or even the cocktail effect? Our approach to these questions is that of material scientists interested in the mechanics of the materials involved rather than that of a tribologist interested in an entire tribological system. Our investigation will begin with CoCrFeMnNi, one of the best characterized fcc high entropy alloys. Over the course of increasing sliding distances and by means of focused ion beam and scanning as well as transmission electron microscopy, we will reveal the elementary mechanisms governing microstructural changes as well as their sequential appearance. CoCrFeMnNi allows to correlate the elementary mechanisms identified during tribological loading to those found in the literature, e.g., for uniaxial tension or compression. The comparison with literature knowledge about the behavior of pure fcc metals and dilute solid solutions will provide insights to the effects which might be exclusive to HEAs. As the alloy’s crystal structure has a decisive impact on how the material behaves under a tribological load, we will start to investigate the bcc model HEA HfNbTaTiZr, during the last year of the requested funding period. It is anticipated that in the near future these results will allow to realize design guidelines for the composition and starting microstructure of HEAs with superior tribological properties.

研究相对运动中相互作用的表面--称为摩擦学--在现代生活中具有重要意义，特别是对于工程部件中普遍使用的金属材料。从材料科学家的角度来看，摩擦学是一个非常有趣的领域，因为亚表面微结构的演变等现象只能从现象上理解。高熵合金(HEAs)是一种新型的金属合金，具有优异的摩擦学性能。关于滑动过程中亚表面显微组织的变化以及导致组织演变的基本机制，目前还没有全面的认识。其中可能起作用的机制包括位错滑移、孪生、剪切带的发展、氧化和机械混合。到目前为止，这种不完整的图景导致了摩擦接触中HEAs的结构-性能关系的缺乏。结合专注于合金开发的海尔迈尔集团和格雷纳集团在材料摩擦学方面的记录，我们的研究将解决三个核心研究问题：(A)高熵合金的初始微结构参数与其摩擦磨损性能之间是否存在明确的相关性？(B)这些基本机制是否与在单轴、单调载荷下获得的基本变形机制相关？(C)这些性质和相互关系能否根据高等教育的独特特征来理解，如严重的晶格扭曲、缓慢的扩散甚至鸡尾酒效应？我们解决这些问题的方法是材料科学家对所涉及材料的力学感兴趣，而不是摩擦学家对整个摩擦学系统感兴趣。我们的研究将从CoCrFeMnNi开始，它是面心立方高熵合金中性能最好的一种。在增加滑动距离的过程中，通过聚焦离子束和扫描以及透射电子显微镜，我们将揭示控制微结构变化的基本机制以及它们的顺序出现。CoCrFeMnNi允许将摩擦学加载过程中确定的基本机制与文献中发现的机制相关联，例如单轴拉伸或压缩。与文献中关于纯面心立方金属和稀固溶体行为的知识进行比较，将提供对可能是HEA所独有的影响的见解。由于合金的晶体结构对材料在摩擦学载荷下的行为有决定性的影响，我们将在申请资助期的最后一年开始研究体心立方模型HEA HfNbTaTiZr。预计在不久的将来，这些结果将允许实现具有优异摩擦学性能的HEA的组成和起始微观结构的设计指南。