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

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).