Superelastic NiTi (Nitinol) alloy is a smart material applied in the biomedical sector for devices, such as stents, implants and orthodontic wires. Nevertheless, after surgery, one of the major causes of failure, which requires the explantation of the device, is linked to bacterial infections. Therefore, development of antibacterial materials becomes an important task in the biomedical field. In this light, the present study investigates the integration of pseudoelasticity of Nitinol withan antibacterial response for realizing advanced implantable devices.

Despite the evident existence of market demand and great efforts in alloy development and processing, non-binary NiTi alloys struggle to exploit their full potential and to satisfy the high expectations from industry. Two exemplary fields of research are low-hysteresis (LH-SMA) and high temperature shape memory alloys (HT-SMA), in which many alloy solutions with promising results were proposed in the last decades, but almost none was commercialized on an industrially relevant scale. The reasons for the limited success might be manifold: Material inherent challenges like creating workable, reliable and performing alloys, cost of setting-up a stable process, trust in new technology, communication between material designer and potential end-user, lack of material provider and further drawbacks obstacle the way to commercialization. Evidentially, existing LH-SMA and HT-SMA solutions suffer a lack of trust from industries to achieve commercial success. Therefore, besides developing material solutions, new ways need to be found to achieve and demonstrate the full potential of the most promising alloys and systems. The here presented research work consists of an assessment of the main obstacles in designing and preparing high-performing ternary and quaternary alloys. The scope is to answer what could be the ideal low hysteresis and high temperature shape memory alloys for industrial commercialization, what are the potentials and limits of commonly used theories and models in material design? What could be suitable demonstrators, experiments and prototypes of simple configurations from a technical point of view in order to convince potential end-users of such novel materials, how could they to be prepared and benchmarked? To be more persuasive, the demonstrator should constitute of an application relevant shape and could be prepared by non-conventional processes if it supports the full exploitation of the material advantages.

In recent years, the interest in shape memory alloys with high transformation temperatures (HTSMA) has significantly increased not only in the academic sphere, but also due to a market-push, especially from aerospace, automotive, and robotics. However, a real break-through has not been achieved yet because of several problems: Lower chemistry control than in NiTi alloys, instability of martensite, decomposition of the matrix phase, brittleness, oxidation, etc. Despite those challenges, steady progress has been made on specific systems and distinct thermo-mechanical treatments have been elaborated to reach promising HT-SMA behavior. Among several systems, Ni-Ti-Hf-Nb emerged as particular promising due to superior mechanical properties of its alloys compared to those of the ternary Ni-Ti-Hf system. In particular, the ductility of Ni-Ti-Hf increases significantly by adding Nb, allowing for formation of a soft eutectic network composed of shape memory matrix phase and a not transforming β-Nb phase at the grain boundaries. Recently, it was demonstrated that by this alloying approach, it is possible to obtain fine wires using conventional drawing techniques, increasing the opportunities for a successful industrial commercialization. In this work, Laser technology was explored for straight annealing of HT-SMA wires and promoting shape memory behavior. The functional performances of laser treated wires were assessed through differential scanning calorimetry (DSC), microstructure analysis, tensile tests and thermal cycling under constant load. Laser parameters were optimized for tailoring transformation properties in order to get a stable transformation at high temperatures, the results were compared to those ones of furnace annealed wires.