Three-dimensional printing of shape memory alloys

NiTi shape memory alloys exhibit interesting mechanical properties, but also poor formability and machinability. Wide applications of SMAs needs efficient manufacturing techniques, especially net-shape solutions.

The aim of this project is to establish the feasibility of manufacturing complex NiTi parts by three-dimensional printing. The parts have been grown by additive layer-by-layer processes, by joining metal powder particles with a polymer binder. The printing step is followed by thermal debinding and sintering in controlled atmosphere. Two routes have been explored: a) printing parts with a ProMetal 3D-printer, which drops binder on powder beds, and b) printing parts with a laboratory printer, which drops solvent on metal-polymer granule beds. Appropriate conditions for layer deposition, printing, debinding and sintering have been established.

3D-printed NiTi specimens exhibit shape memory behaviour. The feasibility of processing complex net-shape prototypes, with good green strength and shape preservation after sintering has been assessed. Further research is necessary to evaluate and improve sintered part properties, dimensional stability, and test functionality.