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Metals 2018, 8(5), 342; https://doi.org/10.3390/met8050342

Manufacturing and Characterization of NiTi Alloy with Functional Properties by Selective Laser Melting

1
Institute of Mold & Die Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 807, Taiwan
2
School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan
3
Division of Oral and Maxillofacial Surgery, Department of Dentistry, Taipei Medical University Hospital, Taipei 110, Taiwan
4
Casting Section, Metal Industries Research & Development Centre, Kaohsiung 811, Taiwan
*
Author to whom correspondence should be addressed.
Received: 18 February 2018 / Revised: 30 April 2018 / Accepted: 8 May 2018 / Published: 11 May 2018
(This article belongs to the Special Issue Machining and Finishing of Nickel and Titanium Alloys)
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Abstract

In this study, an optimal selective laser melting (SLM) process for manufacturing dense NiTi alloy with pseudoelasticity and shape-memory capability was proposed. The microstructure, phase-transformation temperature, shape memory capability, and pseudoelasticity were investigated by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, and bending and tensile tests. NiTi powder with a particle size > 45 μm was selected for the subsequent SLM process, because it exhibited a Ni/Ti ratio of ~1 and a lower oxygen content than powders with smaller particle sizes. A thin-walled disk (0.48 mm thick) and cuboid samples (5 mm thick) were prepared for investigating the variation in the homogeneity of the microstructure. The thin-walled SLM-NiTi sample exhibited a marginally inhomogeneous microstructure between layers, and defects existed in the previously formed side. The cuboid SLM-NiTi sample was fabricated without undesirable secondary phases, and it exhibited a 100% shape-recovery rate under 2% bending strain and completely pseudoelastic under 3% strain. Also, the SLM-NiTi exhibited lower phase-transformation temperatures and a broader phase-transformation range than the original NiTi. The phase-transformation range can be reduced by annealing. View Full-Text
Keywords: selective laser melting; NiTi; shape memory; pseudoelasticity selective laser melting; NiTi; shape memory; pseudoelasticity
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Ou, S.-F.; Peng, B.-Y.; Chen, Y.-C.; Tsai, M.-H. Manufacturing and Characterization of NiTi Alloy with Functional Properties by Selective Laser Melting. Metals 2018, 8, 342.

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