TY - JOUR
T1 - Effect of hatch spacing and laser power on microstructure, texture, and thermomechanical properties of laser powder bed fusion (L-PBF) additively manufactured NiTi
AU - Ehsan Saghaian, Sayed
AU - Nematollahi, Mohammadreza
AU - Toker, Guher
AU - Hinojos, Alejandro
AU - Shayesteh Moghaddam, Narges
AU - Saedi, Soheil
AU - Lu, Charles Y.
AU - Javad Mahtabi, Mohammad
AU - Mills, Michael J.
AU - Elahinia, Mohammad
AU - Karaca, Haluk E.
N1 - Publisher Copyright:
© 2021
PY - 2022/5
Y1 - 2022/5
N2 - This study systematically evaluates the effects of laser powder bed fusion additive manufacturing (L-PBF-AM) parameters (hatch spacing and laser power) on the thermomechanical behavior and microstructure of Ni50.8Ti49.2 shape memory alloy. The samples were fabricated with hatch spacings from 40 to 240 µm and laser powers of 50 and 100 W at a constant scanning speed of 125 mm/s, resulting in parts with volumetric energy density levels from 55 to 666 J/mm3 and two sets of linear energy densities of 0.4 and 0.8 J/mm. The results showed a reduced melt pool size and discontinuity of scan tracks with decreased laser power. Additionally, the porosity level was increased with larger hatch spacing and lower laser power. More notably, the transformation temperatures increased, and the critical stress, recoverable strain, and functional stability of samples improved with lower hatch spacing, where the recovery ratio of up to 90% was observed, regardless of the employed laser power. This study also discussed the relationship between the fabrication process and texture formation in the L-PBF-AM process. The advantage of L-PBF-AM was revealed in tailoring the microstructure from highly textured samples in [1 1 1] or [0 0 1] direction when hatch spacing lower than laser beam focused was employed, to the appearance of equiaxed solidification front with island grains and random orientations.
AB - This study systematically evaluates the effects of laser powder bed fusion additive manufacturing (L-PBF-AM) parameters (hatch spacing and laser power) on the thermomechanical behavior and microstructure of Ni50.8Ti49.2 shape memory alloy. The samples were fabricated with hatch spacings from 40 to 240 µm and laser powers of 50 and 100 W at a constant scanning speed of 125 mm/s, resulting in parts with volumetric energy density levels from 55 to 666 J/mm3 and two sets of linear energy densities of 0.4 and 0.8 J/mm. The results showed a reduced melt pool size and discontinuity of scan tracks with decreased laser power. Additionally, the porosity level was increased with larger hatch spacing and lower laser power. More notably, the transformation temperatures increased, and the critical stress, recoverable strain, and functional stability of samples improved with lower hatch spacing, where the recovery ratio of up to 90% was observed, regardless of the employed laser power. This study also discussed the relationship between the fabrication process and texture formation in the L-PBF-AM process. The advantage of L-PBF-AM was revealed in tailoring the microstructure from highly textured samples in [1 1 1] or [0 0 1] direction when hatch spacing lower than laser beam focused was employed, to the appearance of equiaxed solidification front with island grains and random orientations.
KW - Additive Manufacturing
KW - Effect of Process Parameters
KW - Laser Powder Bed Fusion
KW - NiTi
KW - Shape Memory Alloys
KW - Texture
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U2 - 10.1016/j.optlastec.2021.107680
DO - 10.1016/j.optlastec.2021.107680
M3 - Article
AN - SCOPUS:85120351697
SN - 0030-3992
VL - 149
JO - Optics and Laser Technology
JF - Optics and Laser Technology
M1 - 107680
ER -