Elastocaloric effect of NiTi shape memory alloys manufactured by laser powder bed fusion

Abstract

To address the challenges posed by the complex processing of NiTi alloys, the additive manufacturing technology has been employed for the preparation of NiTi alloys samples. Up to now, there is limited research on the elastocaloric effects of NiTi alloys manufactured by LPBF. This study focused on the utilization of laser powder bed fusion (LPBF) to fabricate NiTi samples, with a particular emphasis on the influence of laser power, scanning speed and hatch spacing on the microstructure and properties of NiTi alloys. The results indicated that the process parameters affect the stress hysteresis of superelasticity by influencing the Ni content in the NiTi alloys. The higher Ni content, the lower the stress hysteresis. In addition, the critical stress for plastic deformation of the texture in the <001> direction in NiTi alloys is the smallest. When only the P was changed, the proportion of the texture in the <001> direction in the sample increased with the increase of P, the proportion of plastic deformation increased, and the degree of recovery also gradually decreased. Furthermore, at a specific temperature, 10 K higher than the end temperature of austenite transformation, each sample exhibited good superelasticity. In particular, the 1st cooling capacity of the sample with the best elastocaloric effect reached 11.0 K, which was superior to other results obtained by LPBF under similar compressive strain levels.