Ni-Ti-Hf-Zr alloys for high-temperature actuation – From material libraries to high-performance functional materials

• Applicant: Professor Dr.-Ing. Thomas Niendorf
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials ; Materials in Sintering Processes and Generative Manufacturing Processes ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 398899207

In the first funding phase, the primary goal was to investigate the relationships between additive manufacturing, microstructural development, and the resulting functional and mechanical properties of Ni-Ti-Hf high-temperature shape memory alloys (HT-SMA). A key challenge in this context was to identify and establish process parameters for the processing of Ni-Ti-Hf HT-SMA (Ni50.5Ti34.5Hf15) using the powder bed fusion - electron beam (PBF-EB/M) process, and finally to adjust the microstructure in the process by varying these parameters. Due to the very high price of hafnium, increasing the transformation temperatures by increasing Hf contents in this alloy system currently does not seem to be economically viable. For this reason, in the second funding phase, the element zirconium will be mixed into the base alloy in defined fractions using a novel approach in order to increase the transformation temperatures and, at the same time, functional performance. This project will use an innovative approach using a directed energy deposition system (High-throughput material characterization using laser deposition additive manufacturing combined with high-flux in situ X-Ray analysis enhanced by further instrumentation to realize alloy screening using the base alloy and elemental powders. The goal of the proposed alloy design is to exploit the high-throughput approach to characterize a large number of additively manufactured specimens of varying chemical compositions and, eventually, to significantly and cost-effectively increase the transformation temperatures in the quaternary Ni-Ti-Hf-Zr system.

• DFG Programme: Research Grants