In this work, nitinol samples were produced via Laser Powder Bed Fusion (L-PBF) in the horizontal and
vertical orientations with systematic variations in laser power, scan speed and hatch spacing parameters.
Increased density was positively correlated with increased laser power, scan speed and hatch spacing for
the horizontally built samples but not for the vertically built samples. A smaller difference in the average
temperature within a printed layer, associated with the vertically built samples, was linked with reduced
porosity and reduced porosity variability between samples. Control of the L-PBF parameters was found to
allow control of the resulting part chemical composition which also directly affected phase transforma-
tion temperatures, and related phase structures. The laser process parameters were found to have a sig-
nificant effect (p < 0.01) on the martensite start/finish temperature, austenite start/finish temperatures,
and the total temperature span. The volumetric energy density was also found to have a direct correlation
with both the cooling (r = 0.52) and heating (r = 0.53) enthalpies, which was found to be due to increased
nickel evaporation. Such control of phase change properties afforded from L-PBF is important for many of
the end applications for nitinol components including within the energy and precision actuation sectors
Item Type:
Article (Published)
Refereed:
Yes
Additional Information:
Article number: 110715
Uncontrolled Keywords:
Nitinol; Process optimisation; powder bed fusion; Phase transformation; Shape memory effect; Differential Scanning Calorimetry (DSC)