Prospects and challenges in additive manufacturing of shape memory alloys

Shape memory alloys (SMAs) are characterized by unique properties stemming from a fully reversible phase transformation between a high-temperature austenitic phase and a low-temperature martensitic phase. Depending on the alloy composition and the actual loading condition, specific effects can be exploited: the shape memory effects and superelasticity. Conventionally processed SMAs are used in numerous applications, however, SMAs processed by any kind of additive manufacturing (AM) technique still suffer roadblocks toward application. The present paper highlights most important findings elaborated in recent years. Focus will not only be on the general processability of SMAs in AM, but also on apt microstructure design and functional/structural degradation. Here, it will be shown that the unique characteristics of AM are beneficial to obtain highly anisotropic microstructures that are desired for superior shape memory properties. At the same time gradient microstructures can be established paving the way toward novel actuator designs. Based on the results presented, future prospects and prevailing challenges, respectively, will be thoroughly discussed.