Microstructure evolution during processing and mechanical properties of high-entropy alloys

该项目将专注于开发、加工和理解由粉末基工艺制造的高熵合金（HEAs），该工艺允许直接制造近净形状部件。高熵合金是一个术语，适用于一种相对较新的金属合金系统，它包含至少三种或三种以上合金元素的接近等原子浓度。HEAs的一个令人惊讶的特点是，尽管它们的组成看起来很复杂，但它们通常由完整或接近简单的固溶体组成。自从2004年发现这些合金以来，大量的这些合金被小规模制造，它们的结构和性能在科学文献中得到了报道。虽然它们在技术上还不成熟，但一些数据已经显示出一些有趣的、有吸引力的特性组合，比如在低温下的超高韧性，以及在室温下前所未有的高拉伸延展性和高断裂强度的组合。此外，可能的等原子组合物的组合是巨大的，仍然未被探索，为开发具有优异性能的新组合物提供了巨大的潜力。该项目将调查一些最有前途的组合物的可加工性和可制造性，旨在为工业应用开发示范。该项目将有以下目标：-将HEA的生产规模扩大到更高的trl，开发HEA粉末加工一步制造路线，用于制造复杂形状的部件，同时使用烧结（固态）和3D打印（液态）；-开发具有新增强性能的复杂形状HEA工业示范；-调查工艺参数与性能之间的关系；-研究新的HEA成分。该研究将首先研究基于相对知名的FeNiCrMnCo合金的成分对结构和性能的影响，该合金使用场辅助烧结技术（FAST）和最先进的3D打印技术从粉末加工成大块。性能评估将集中在不太了解的低温特性和耐辐照性上，这些可以通过实验室离子辐射实验与合作者进行研究。学生们将首先用简单的圆柱几何形状制造典型的小样品，随后，工作将集中在生产近净形状部件的工艺开发上。从管子开始，然后是越来越复杂的几何形状。最后，工作还将着眼于新的组合物，包括轻质HEAs，以及添加少量有效分散增强材料的可能性。到目前为止，HEAs的研究重点是新的组成和性能表征。该项目的新颖之处在于，通过为选定数量的有前途的合金开发加工路线，并制造具有复杂形状的样品，扩大了HEAs的生产规模，并在更高trl下开放了HEAs的使用。此外，将探索使用结合3D打印和烧结的新工艺来“功能化”组件以扩展其性能的可能性，这增加了项目的独创性。这项工作属于EPSRC未来制造和工程研究领域，也将与MAPP: EPSRC未来制造中心使用先进粉末工艺制造（EP/P006566/1）保持一致。

The project will focus on the development, processing and understanding of high entropy alloys (HEAs) manufactured by powder based processes that allows near-net shape components to be fabricated directly. High entropy alloy is a term applied to a relatively new type of metallic alloy system that comprises near equiatomic concentrations of at least three or more alloying elements. A surprising characteristic of HEAs is that despite their apparent compositional complexity, they comprise usually a complete or near simple solid solution. Since their discovery in 2004 a large number of these alloys have been manufactured at small scale and their structure and properties reported in the scientific literature. Although they are still technologically immature some data has shown intriguing and attractive combinations of properties, such as ultra-high toughness at cryogenic temperatures and unprecedented combination of high tensile ductility and high fracture strength at room temperature. Furthermore, the combinations of possible equiatomic compositions are enormous and still unexplored offering huge potential to develop new compositions with outstanding properties. The project will investigate the processability and manufacturability of some of the most promising compositions aiming at develop demonstrators for industrial applications. The project will have the following objectives:- Scale-up production of HEAs to higher TRLs developing a HEA powder processing one-step manufacturing route for the fabrication of complex shaped component, both using sintering (solid state) and 3D priting (liquid state);- Develop industrial demonstrators of complex shape HEA with new enhanced properties;- Investigate relationship between processing parameters and properties;- Investigate new HEA compositions.The research will initially investigate composition effects on structure and properties based around the relatively well-known FeNiCrMnCo alloy, processed from powders to bulk using field assisted sintering technique (FAST) and state of the art 3D printing. The property assessment will focus on the less well-understood cryogenic properties and resistance to irradiation that can be studied by laboratory ion radiation experiments with collaborators. The students will initially manufacture typically small sample with simple cylindrical geometry, subsequently, the work will focus on the development of a process to produce near-net shape components. Starting from a tubes and then with increasing complex geometry. Finally work will also look at new compositions, including light-weight HEAs, and the possibilities of adding minor fractions of potent dispersion strengthening materials.So far the focus of the research on HEAs has been on new compositions and properties characterization. The novelty of this project resides in scaling up production and open the use of HEAs at higher TRLs by developing a processing route for a selected number of promising alloys and fabricating demonstrators with complex shape. Furthermore, the possibility of 'functionalize' components to extend their properties using a novel processing which combine 3D printing and sintering will be explored, which adds to the originality of the project. The work falls within the EPSRC Manufacturing the future and Engineering research areas and will also be aligned with the MAPP: EPSRC Future Manufacturing Hub in Manufacture using Advanced Powder Processes (EP/P006566/1).