Exploitation of transition temperatures of NiTi- SMA by adjusting SLM parameters

It is well known that the transition temperatures, e.g. the austenite peak temperature Ap, of NiTi Shape Memory Alloys (SMAs) can be adjusted by changing the alloy composition. This topic recently became more interesting due to the possibilities to produce SMA-parts by additive manufacturing, specifically by Selective Laser Melting (SLM). The potential of new designs and smart structures by so-called 4D-printing with locally adjusted transition temperatures Ap potentially opens up new applications and novel temperature-responsive medical devices. This work focuses on the SLM manufacturing parameters exposure time ET (scanning speed) and laser power P and their impact on the transition temperature Ap beyond the commonly used generic process parameter energy density ED. By systematical variation of process- and scan-parameters, the impact of the P, ET, sample orientation and layer height LH as well as interdependencies between them have been studied. A wide range of transition temperatures Ap between -20°C and 70°C has been reached from one starting material by varying ET. These findings potentially allow the manufacturing of smart devices with multi-stage deformation processes in a single 4Dprinted part.