Influence of laser cycling on electro-structural features of nickel-titanium SMA fabricated by LPBF process

Abstract

The effect of laser cycling and tempering on structural heterogeneity and electro-structural properties of 2D layers and 3D multilayers of nickel-titanium intermetallide during the laser powder bed fusion (LPBF) process has been studied by the authors and is offered below. Besides, the expediency of the laser melting and solidification parameters tuning, implementation of preliminary and subsequent laser tempering is proved by the final state of the shape memory alloy (SMA). It is shown that specific electrical resistivity (SER) of the studied phases (austenite, R-phase, martensite) abnormally varies with temperature. During a high-speed laser cooling, SER increases in two stages, and the first pre-martensite stage is accompanied by structural heterogeneity growth and corresponds to the intermediate R-phase formation. Electro-structural features of the 3D printed NiTi are almost 2–3 times higher than those of melted 2D monolayers.Varying structural heterogeneity by changing the laser influence (LI) parameters and/or heat treatment allows us to get a material with different functional properties. It can be used both in medicine for approximating SME to the human body temperature, and also in high-temperature applications, for example, as dampers.