High-strength superelastic Ti–Ni microtubes fabricated by sputter deposition |
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Authors: | Pio John S. Buenconsejo Kanau Ito Hee Young Kim Shuichi Miyazaki |
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Affiliation: | aInstitute of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan |
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Abstract: | Ti–Ni microtubes are attractive materials for biomedical devices, such as micro-catheters and micro-stents, but it is difficult to fabricate them with dimensions of less than 100 μm by conventional tube-drawing. In this study, Ti–Ni microtubes with 50 μm inner diameter and a tube wall thickness of 6 μm was successfully fabricated using a novel method in which Ti–Ni was sputter-deposited on a Cu wire with a diameter of 50 μm. All the microtubes exhibited shape memory behavior after crystallization at 873 K for 3.6 ks. Microtubes fabricated without rotating the Cu wire during deposition have low fracture strength due to the columnar grains and non-uniform tube wall thickness. Microtubes fabricated by depositing Ti–Ni on a rotating wire have a uniform wall thickness and the fracture strength increased with increasing rotation speed. Microtubes made by the rotating-wire method exhibited superelasticity of 3% strain at room temperature with high fracture stress of 950 MPa, suggesting that they are suitable for practical applications. |
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Keywords: | Ti–Ni Shape memory alloys Sputter deposition Microtubes Thin films |
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