Development of NiTi-based SMA niche applications by customized alloying and production strategies for microstructure engineering

For almost three decades, Nitinol has been established in the medical market. Nitinol components are well known due to their extraordinary properties like superelasticity. Today, NiTi is used in a wide variety of medical devices or implants and a billion-dollar market has grown around this special metal, along with industrial standards for the production, testing and quality. However, the commercial success in the medical field is dwarfed by the still unused potential of SMA applications in other areas.

Several reasons have led to this unequal distribution of SMA in favor of the medical field. One is that service conditions are rather constant and can be met with a single alloy. Actuators are far more complicated and alloys available today only meet a small fraction of the properties required for different applications. NiTi is not enough in the light of a much-needed customization of phase transition temperatures or hysteresis widths. Other important factors like proper dimensioning of actuators or the development of suitable electronic controllers are still not standardized, and the literature on these topics is of little to no help to beginners. Beside these materials-based issues, the SMA community has to acknowledge the rules of new markets in order to become a valid alternative to established solutions like wax elements. With an example of NiTi(X,Y)-actuators, we show how we replaced a non-SMA solution in the automotive industry, transferring our lab-based research results from the SFB 459 to the establishment of Germany’s first fully integrated production line of shape memory alloys.