Title:
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Mechanical and microstructural characterization of new nickel-free low modulus beta-type titanium wires during thermomechanical treatments
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Author:
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Guillem Martí, Jordi; Herranz-Diez, Carolina; Shaffer, J.E.; Gil Mur, Francisco Javier; Manero Planella, José María
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Notes:
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NiTi alloy is the only practical shape memory alloy (SMA) in biomedical use because of its excellent mechanical stability and functionality. However, it is estimated that between 4.5% and 28.5% of the population are hypersensitive to nickel metal, with a higher prevalence in females. Therefore, developing nickel-free low modulus beta-type titanium alloys showing shape memory or super elastic behavior would have a great interest in the biomaterials field. Homogeneous 127 mu m diameter Ti25Hf21Nb wires were produced and compared to straight annealed Ti-50.8 at% Ni (Nitinol) and 90% cold-drawn 316L wires. Microstructural changes taking place during the heat treatment of cold-worked Ti25Hf21Nb wires were investigated. Large plastic deformation during wire drawing and subsequent annealing led to nano-crystallization and amorphization which may contribute to the observed superelasticity. Mechanical properties were characterized using cyclic uniaxial tension and rotary beam fatigue test modes. A modulus of elasticity of less than 60 GPa and axial recoverable strain of greater than 3% were observed with stress hysteresis resembling a reversible stress-induced martensitic transformation at higher temperatures. The new Ti25Hf21Nb alloy is an important candidate for developing Ni-free SMAs in the future. |
Subject(s):
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-Aliatges -Elasticitat -Materials biomèdics -Titani -- Aliatges -Aleaciones -Elasticidad -Materiales biomédicos -Titanio -- Aleaciones -Alloys -Elasticity -Biomedical materials -Titanium alloys -62 |
Rights:
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© 2015 Elsevier B.V. All rights reserved. |
Document type:
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Article Article - Accepted version |
Published by:
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Elsevier
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