Direct microstructure design enabled by additive manufacturing of magnetic shape memory Ni-(Co)-Mn-Sn Heusler alloys for multicaloric applications

• Applicants: Professor Dr.-Ing. Thomas Niendorf; Dr. Franziska Scheibel
• Subject Area: Materials in Sintering Processes and Generative Manufacturing Processes ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 527201505

In the present project the microstructural and magnetic properties of Ni (Co)-Mn-Sn Heusler shape memory alloys (SMAs) will be specifically designed for multicaloric solid-state cooling using the directed energy deposition (DED) process. With respect to the microstructure, a highly textured bamboo-like structure is aimed for, eventually maximizing mechanic and cyclic stability. Doping of Ni-Mn-Sn by Co and Fe elemental powders will be accomplished to design the magnetic properties and enhance cyclic stability, respectively. In this regard, the DED process allows for a precise in process alloying of small amounts of elemental powders, i.e., Co and Fe. A novel DED setup available in Kassel enables high-throughput characterization of materials being in situ alloyed with small amounts of the Fe (first step) and Co (second step) powders. The DED machine is equipped with further instrumentation for high-throughput analysis, such as X-ray tomography and diffraction in order to collect data directly during processing, eventually supporting an efficient process parameter identification. To achieve maximum mechanical and cyclic stability for the chemical compositions processed, the porosity, the occurrence of hot cracks and other defects must be minimized. Post-process heat treatments will be used for homogenization and further affect magnetic ordering. Besides the mechanical (pseudoelastic (PE) and shape memory effect (SME)) and magnetic properties as well as the associated caloric effects, which will be characterized in depth, the DED processed alloy is investigated using a multi-stimuli test-bed to finally assess the cyclic multicaloric performance.

• DFG Programme: Research Grants