Abstract
NiTiCu alloys are one of the most investigated shape memory alloys (SMAs) because of their better performance as SMA actuators in a variety of industrial and engineering applications. However, NiTiCu alloys are strongly influenced by thermomechanical cycling (TMC), which causes degradation depending on the stress and strain level applied. Since heat treatment (HT) and TMC are essential for NiTiCu alloys, understanding how hardness evolves at different levels of TMC and different HT temperatures is a useful tool for characterizing the material. The aim of this paper is to investigate the relationship between hardness and different HT temperatures and different TMCs. All the microhardness tests were done below martensite finish temperature (Mf) because the apparent material hardness measured below Mf fairly reflects the relative strengthening of SMAs without involving martensitic transformation artifacts. Resistivity and break tensile tests were carried out as a first step in order to understand the effect of different HT temperatures. Microstructure was also examined to provide a basis for a mechanistic understanding of the effect of different HT temperatures. Next, the degradation of mechanical properties (functional fatigue) at different levels of TMC was evaluated to assess their relationship to the evolution of hardness. Finally, an attempt was made to establish a link between the increase in hardness and different HT temperatures with different levels of TMC.
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References
K. Otsuka and C.M. Wayman, Shape Memory Materials, Cambridge University Press, Cambridge, 1998
C. Urbina, Improvement of the One-Way and Two-Way Shape Memory Effects in Ti-Ni Shape Memory Alloys by Thermomechanical Treatment, Ph.D. Thesis, Universitat Rovira i Virgili, 2011. http://hdl.handle.net/10803/37358. Accessed 27 Sept 2013
S. De la Flor, C. Urbina, and F. Ferrando, Effect of Mechanical Cycling on Stabilizing The Transformation Behaviour of NiTi Shape Memory Alloys, J. Alloys Compd., 2009, 469, p 343–349
A.R. Pelton, S.M. Rusell, and J. DiCello, The Physical Metallurgy of Nitinol for Medical Applications, JOM, 2003, 55, p 33–37
A. Nespoli and S. Besseghini, A Complete Thermo-mechanical Study of a NiTiCu Shape Memory Alloy Wire, J. Therm. Anal. Calorim., 2011, 103, p 821–826
D. Vojtěch and A. Michalcová, Influence of Heat-Treatment on Mechanical Properties and Transformation Temperatures of Nitinol, Key Eng. Mater., 2011, 465, p 471–474
F.T. Cheng, On the Indeterminacy in Hardness of Shape Memory Alloys, J. Mater. Sci. Technol., 2004, 20, p 700–702
V. Brailovski, P. Terriault, and S. Prokoshkin, Influence of the Post-deformation Annealing Heat Treatment on the Low-Cycle Fatigue of NiTi Shape Memory Alloys, J. Mater. Eng. Perform., 2002, 11, p 614–621
A. Fabregat-Sanjuan, F. Ferrando, C. Urbina, and S. De la Flor, TiNiCu Martensitic Transformation Characterization at Low Stress Levels Through Thermomechanical Cycling, Mater. Sci. Forum, 2013, 738-739, p 367–371
C.P. Frick, A.M. Ortega, and J. Tyber, A.EI.M. Maksound, H.J. Maier, Y. Liu, K. Gall, Thermal Processing of Polycrystalline NiTi Shape Memory Alloys, Mater. Sci. Eng. A, 2005, 405, p 34–49
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This article is an invited paper selected from presentations at the International Conference on Shape Memory and Superelastic Technologies 2013, held May 20-24, 2013, in Prague, Czech Republic, and has been expanded from the original presentation.
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Fabregat-Sanjuan, A., Ferrando, F. & De la Flor, S. NiTiCu Shape Memory Alloy Characterization Through Microhardness Tests. J. of Materi Eng and Perform 23, 2498–2504 (2014). https://doi.org/10.1007/s11665-014-1099-0
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DOI: https://doi.org/10.1007/s11665-014-1099-0