FOR 1766:  High-Temperature Shape Memory Alloys - From Basics to Applications

• Subject Area: Materials Science and Engineering
• Term: from 2012 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 200999873

Lately, high-temperature shape memory alloys (HT-SMA) have attracted a lot interest both from academia and industry. Given their unique properties new products are easy to envision that have impact for the manufacturing, aerospace and automotive industries. Unfortunately, the commercially available conventional SMAs have low transformation temperatures and the HT-SMAs developed so far typically rely on substantial amounts of expensive elements such as palladium. Moreover, new alloys will only be used commercially, if they do not only possess attractive properties, but have been characterised and tested such that a validated prediction of their behaviour under actual loading conditions is feasible. Consequently, the objective of the Research Unit is to develop microstructurally stable HT-SMAs that are based on cheap constituents, and at the same time provide for a validated material model that allows for life prediction under service loading. The initial focus of the Research Unit will be on screening of promising alloys using a combinatorial materials science approach. Next, both modelling and experiments will be employed to generate a comprehensive data set for the alloys that have been identified as potential HT-SMAs. Currently, Co-Ni-X and Ti-Ta-X appear to be the most promising candidate systems. Co-Ni-X is known to provide for high-temperature pseudoelasticity and Ti-Ta-X is of interest for high-temperature actuation. The relevant microstructural mechanisms that control microstructural stability in these systems are, however, not clear yet. Currently, microstructural stability under cyclic loading at high-temperature is a major road block for the use of HT-SMAs. Ultimately, the objective of the Research Unit is to realise a cyclically stable HT-SMA component that makes use both of SMA actuation and damping and also demonstrates that such parts can be produced in an industrial relevant process. This would constitute a major breakthrough for HT-SMAs and could make them as successful in new technological areas as conventional SMAs are today in the biomedical niche.

• DFG Programme: Research Units

Projects

• Central project: Coordination of the research unit (Applicant Maier, Hans Jürgen )
• Combinatoric alloy development, casting and thermomechanical Optimization of high-temperature shape memory alloys (Applicants Frenzel, Jan ;  Ludwig, Alfred )
• Experimental and theoretical investigations of the structure and the properties of Ti-Ta-X-Y and Co-Ni-Ga-X high-temperature shape Memory alloys: Syncrotron and Neutron diffraction and atomistic modelling (Applicants Rogal, Jutta ;  Schmahl, Wolfgang W. )
• Functional stability of polycrystalline Co-Ni-Ga high-temperature shape-meory alloys - On the role of microstructure and martensite stabilization (Applicants Frenzel, Jan ;  Maier, Hans Jürgen ;  Niendorf, Thomas )
• On the role of precipitates and lattice defects in the martensitic transformation of high temperature shape memory alloys (HT SMAs) (Applicants Eggeler, Gunther ;  Somsen, Christoph )
• Thermomechanical Fatigue of Ti-Ta-X-Y High-Temperature Shape Memory Alloys: Cyclic Stress-Strain Response and Damage Evolution (Applicants Maier, Hans Jürgen ;  Schmahl, Wolfgang W. )

• Spokesperson: Professor Dr.-Ing. Hans Jürgen Maier