Shape memory alloys (SMAs) represent a class of smart materials that attracted significant attention for efficient solid-state actuation and damping applications. While binary Ni-Ti, currently the most widely employed SMA, features excellent functional properties, the inherent application temperature limit of about 80 °C hinders its technological breakthrough in fields like the aerospace and energy sectors, where operating temperatures often exceed 100 °C. In order to extend the application temperature range, so-called high-temperature (HT-)SMAs featuring increased martensite start temperatures (Ms) have been designed in the last decades. Among the numerous HT-SMA candidates introduced so far, Ti-Ta alloys are considered as promising materials due to their relatively high Ms temperatures combined with excellent workability and transformation strains in polycrystalline state of up to ~4%. However, the fabrication via conventional processing routes is still time-consuming and cost-intensive. In particular, the realization of a homogeneous distribution of the constituents is highly challenging due to the differences in the melting points and densities of the alloying elements. In this regard, additive manufacturing (AM) recently came into focus as a new processing route, being capable to fabricate refractory titanium alloys.

In the present work, it is shown that near-fully dense Ti-Ta HT-SMA parts with superior chemical homogeneity can be obtained by powder bed-based AM techniques, i.e. electron (PBF-EB/M) and laser beam powder bed fusion (PBF-LB/M), using novel pre-alloyed feedstock material. An in-depth microstructure analysis along the whole process chain, i.e. from powder material to additively manufactured bulk structures, was conducted employing optical and scanning electron microscopy, computed tomography and X-ray diffraction. Interrelationships between (process-induced) microstructure, martensitic transformation behavior and functional properties are elaborated and discussed.