Effect of hatch spacing and laser power on microstructure, texture, and thermomechanical properties of laser powder bed fusion (L-PBF) additively manufactured NiTi

Sayed Ehsan Saghaian, Mohammadreza Nematollahi, Guher Toker, Alejandro Hinojos, Narges Shayesteh Moghaddam, Soheil Saedi, Charles Y. Lu, Mohammad Javad Mahtabi, Michael J. Mills, Mohammad Elahinia, Haluk E. Karaca

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

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.

Original languageEnglish
Article number107680
JournalOptics and Laser Technology
Volume149
DOIs
StatePublished - May 2022

Bibliographical note

Funding Information:
The authors acknowledge and appreciate the financial support of Ohio Federal Research Network. In addition to partial support from DOE Grant DE-SC0001258.

Funding Information:
The authors acknowledge and appreciate the financial support of Ohio Federal Research Network. In addition to partial support from DOE Grant DE-SC0001258. Data Availability, The raw/processed data of this study are available from the corresponding author, [SES], upon reasonable request.

Publisher Copyright:
© 2021

Keywords

  • Additive Manufacturing
  • Effect of Process Parameters
  • Laser Powder Bed Fusion
  • NiTi
  • Shape Memory Alloys
  • Texture

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering

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