New Quinary and Senary High Entropy Shape Memory Alloys (HE-SMA) – Exploring and Exploiting Martensitic Transformations and Shape Memory Effects in Chemically Complex Systems

建议的研究集中在理解和开发控制高熵形状记忆合金(HE-SMA)行为的机制。长期目标是建立这些材料作为一类新的工程合金，具有广泛应用的潜力。这项拟议的研究有三个科学目标。合金开发活动基于一种新的筛选方法，以开发新的五元和四元形状记忆合金。这种持续的背景活动涉及高精度的熔化活动，并解决了研究钢锭冶金加工链上的微观组织演变的必要性，包括(I)控制高温熔体的凝固和(Ii)在铸造后热机械处理过程中发生的过程。这三个科学目标可以简单地描述如下：第一，确定新的组份，在相变温度高、形状记忆应变大和功能稳定性方面优于传统的SMA。其次，使用先进的表征方法(除了标准方法：先进的分析型高分辨率扫描电子显微镜、原子探针断层扫描仪)来阐明化学复杂性对支配和影响马氏体相变的基本相变和形变过程的影响。第三个目标是推进形状记忆技术。该部分重点研究了化学复杂性对形状记忆效应(单向效应、伪弹性)的影响，旨在开发一种能够评价和量化弹簧驱动器功能性能的HE-SMA演示器。在拟议工作的基础部分，将高熵合金和形状记忆合金这两个引人入胜的研究领域的公开问题联系在一起。具体地说，将探索化学复杂性如何影响HE-SMA的机械和功能性能，以及如何利用化学复杂性来促进HE-SMA技术。从技术角度来看，挤压加工将应用于成分复杂的HE-SMA，这有望提供进一步提高延展性的材料。此外，还将建造和表征弹簧致动器，特别关注功能疲劳，这限制了所有形状记忆合金的可开发使用寿命。本提案中提议的工作方案细分为11个定义明确的一揽子工作方案，其中一个专门讨论与其他战略文件编制项目的互动。

The proposed research focusses on understanding and exploiting the mechanisms that govern the behavior of high entropy shape memory alloys (HE-SMAs). The long-term objective is to establish these materials as a new class of engineering alloys, which have potential for wide spread applications. Three scientific objectives characterize the proposed research. The alloy development activity is based on a novel screening approach in order to develop new quinary and senary shape memory alloys. This continuous background activity involves high precision melting activities and addresses the need to study the microstructural evolution along the ingot metallurgy processing chain, including the processes that (i) govern the solidification of senary melts and (ii) occur during post-cast thermo-mechanical treatments. The three scientific objectives can be briefly described as follows: Firstly, to identify new compositions for HE-SMAs that outperform conventional SMAs in terms of high transformation temperatures, large shape memory strains and good functional stability. Secondly, to use advanced characterization methods (in addition to standard methods: advanced analytical high-resolution SEM and TEM, atom probe tomography) to clarify the effect of chemical complexity on the elementary transformation and deformation processes that govern and affect the martensitic phase transitions. The third objective aims at advancing shape memory technology. This part focuses on studying the influence of chemical complexity on the relevant shape memory effects (one-way effect, pseudoelasticity) and aims at developing a HE-SMA demonstrator, which allows appreciating and quantifying the functional performance of a spring actuator. In the fundamental part of the proposed work, open questions from the two fascinating research areas high entropy alloys and shape memory alloys are linked. Specifically, the way in which chemical complexity affects mechanical and functional properties of HE-SMAs and how chemical complexity can be exploited to promote HE-SMA technology will be explored. From a technological point of view, extrusion processing will be applied to compositionally complex HE-SMAs, which promises to provide materials with further increased ductility. Moreover, a spring actuator will be built and characterized, with a special focus on functional fatigue, which limits the exploitable service life of all shape memory alloys. The work programme proposed in this proposal is subdivided into 11 well-defined work packages, one of which is devoted to the interaction with other SPP projects.