High-throughput experimental and Calphad screening of CCAs (Hi-TeCC) - towards new alloys with exceptional mechanical properties

在过去的13年里，多主元素合金（MPEAs）的发展为新型材料的设计打开了一扇新的机会之窗。MPEAs可以细分为单相高熵合金（HEAs）和多相成分复杂合金（CCA）。MPEA包含五个或更多的主要元素，而不是构成一个基本元素。因此，可能的化学成分和性质的巨大空间变得可用，这刺激了该领域的深入研究。然而，由于可能的合金系统数量非常多，到目前为止只能研究一小部分。更令人担忧的是，大多数可能适用于结构应用的单相无序HEAs的机械性能无法与现有的钢和镍基合金竞争。因此，通过从单相HEAs到多相CCA的发展来进行沉淀/多相硬化是改善这些合金的机械性能的有希望的途径。这开辟了一个迄今为止尚未探索的机会的广阔领域。为了探索和最佳地利用HEAs和CCA，结合高通量热力学模拟和实验的广泛的合金筛选方法是不可避免的。该提案描述了一项满足上述问题的研究战略。它也符合SPP 2006“成分复杂合金-高熵合金”的目标，并做出了很大贡献。我们将使用一种方法，允许高通量的计算和实验筛选的HEAs/CCA，并促进更容易设计新的合金系统。热力学建模将包括数据库的开发和作为可靠的Calphad计算基础的单个三元系统的评估。合适的化学成分将从Calphad数据确定，以开发有前途的多相CCA。通过使用元素粉末混合物的激光金属沉积（LMD）进行快速合金开发，将实现具有高化学均匀性的散装材料的高吞吐量生产。通过第一筛选步骤确定的有前途的合金将通过对微观结构演变和机械性能的彻底表征进行深度筛选。最后，最有前途的合金也将通过铸造、轧制和退火等常规工艺生产，以证明大批量生产的可行性。我们将专注于添加Al和/或C的Co-Cr-Fe-Mn-Ni系统，以扩展该合金系统，并允许从单相HEAs向多相CCA发展。一方面，这种方法将使我们能够开发一个更好的基本热力学描述，并获得影响HEAs和CCA的机械性能的微观结构特征的基本理解。另一方面，HEAs向CCA的扩展使得基于HEAs概念的新型先进结构材料的设计标准能够以应用为导向进行评估。

During the past 13 years a new window of opportunity for the design of novel materials was opened by the development of alloys with multi principal elements (MPEAs). MPEAs can be subdivided into single-phase high-entropy alloys (HEAs) and multi-phase compositionally complex alloys (CCAs). Instead of constituting one base element, MPEAs contain five or more principal elements. Hence, a vast space of possible chemical compositions and properties became available, which stimulated intensive research in this field. However, due to the very high number of possible alloy systems, only a small fraction could be investigated so far. Even more alarming, most single-phase, disordered HEAs potentially suitable for structural applications have mechanical properties that cannot compete with established steels and Ni-base alloys. Therefore, precipitation/multi-phase hardening by advancing from single-phase HEAs to multi-phase CCAs is a promising path to improve the mechanical properties of these alloys. This opens a vast field of hitherto unexplored opportunities. In order to explore and make optimal use of HEAs and CCAs, an extensive alloy screening approach, combining high-throughput thermodynamic simulations and experiments is inevitable. This proposal describes a research strategy that meets the issues mentioned above. It also fits and contributes very well to the objectives of the SPP 2006 "Compositionally Complex Alloys - High Entropy Alloys". We will use a methodology that allows high-throughput computational and experimental screening of HEAs/CCAs and facilitates easier design of new alloy systems. Thermodynamic modeling will include development of databases and evaluation of individual ternary systems as a basis for reliable Calphad calculations. Suitable chemical compositions will be determined from Calphad data in order to develop promising multi-phase CCAs. High-throughput production of bulk material with high chemical homogeneity will be performed by rapid alloy development using laser metal deposition (LMD) of elemental powder blends. Promising alloys identified by the first screening step will be subjected to deep screening by thorough characterization of the microstructure evolution and mechanical properties. Finally, the most promising alloy will also be produced following conventional processing by casting, rolling, and annealing to prove producibility in large quantities. We will focus on the Co-Cr-Fe-Mn-Ni system with additions of Al and/or C to extend this alloy system and allow for advancing from single-phase HEAs to multi-phase CCAs. On the one hand, this approach will allow us to develop a better fundamental thermodynamic description and gain a basic understanding of the microstructural features that influence the mechanical properties of HEAs and CCAs. On the other hand, the extension of HEAs towards CCAs enables an application-oriented assessment of design criteria for new advanced structural materials based on the concepts of HEAs.