Effect of cold deformation to transformation temperatures of Ni-Ti shape memory alloys

• Autorzy: Yildiz C. , Kucukyildirim B. O. , Akdogan Eker A.
• Języki publikacji: EN

Abstrakty

EN

Purpose: of this paper is to predict the effect of cold deformation to transformation temperatures of Ni–Ti SMA and clarify the relation between cold forming ratio and the parameters of thermo mechanical process. Design/methodology/approach: 25% and 50% cold formed Ni–Ti wire specimens are investigated for defining the relation between the ratio and the parameters of thermo mechanical processes of without annealing and with annealing at 450°C for 30 minutes and 600°C for 30 minutes. Moreover, Differential Scanning Calorimeter (DSC) measurements are applied to the specimens for obtaining the transformation temperatures. Findings: According to DSC measurements, start and finish temperatures of transformation of austenite, martensite and rhombohedral phases are calculated. Hence, their changes are related to deformation and annealing, so it can be implied that cold deformation process leads to increases in the temperature ranges, slow occurrences of transformation and also the shape memory property lowers. Research limitations/implications: It is observed that some specimens exhibit rhombohedral phase transformation and this affects the martensite phase transformation temperatures and results. Thus, annealing time can be increased to determine both positive and negative effect to transformation properties for further research. Moreover, the grainsize and form may also be effective, so this case should be studied. Practical implications: can be stated as suitable transformation temperatures must be paid attention to desired service temperatures of products those are made of Ni–Ti SMAs, otherwise they may exhibit unexpected shape change due to the affected transformation temperature. Originality/value: is that Ni–Ti SMAs may be exposed to cold deformation when they are manufactured for being given any product shape, so with this research it can be determined that if their transformation temperatures change or not. Besides, it can be implied that they change and so this study presents the changes, the intervals of start and finish temperatures relevant to the cold forming ratio.

Słowa kluczowe

EN

shape memory alloy; SMA; titanium-nickel alloy; cold forming; transformation temperature

PL

stop z pamięcią kształtu; SMA; stop tytanowo-niklowy; formowanie na zimno; temperatura przemian

• Wydawca: International OCSCO World Press
• Czasopismo: Archives of Materials Science and Engineering
• Rocznik: 2014
• Tom: Vol. 66, nr 1
• Strony: 37--44
• Opis fizyczny: Bibliogr. 7 poz.

Twórcy

autor

Yildiz C.

• Department of Mechanical Engineering, Yildiz Technical University, Besiktas, Istanbul, 34349, Turkey

autor

Kucukyildirim B. O.

• Department of Mechanical Engineering, Yildiz Technical University, Besiktas, Istanbul, 34349, Turkey

autor

Akdogan Eker A.

• Department of Mechanical Engineering, Yildiz Technical University, Besiktas, Istanbul, 34349, Turkey

Bibliografia

• [1] T. Sakuma, Y. Mihara, H. Toyama, Y. Ochi, K. Yamauchi, Effect of cold working on transformation and deformation behavior after pre-deforming in Ti-50 at %Ni shape memory alloy, Materials Transactions 47 (2006) 787-791.
• [2] S.A. Thompson, An overview of nickel-titanium alloys used in dentistry, International Endodontic Journal 33 (2000) 297-310.
• [3] D.E. Hodgson, M.H. Wu, R.J. Biermann, Shape memory alloys, Metals Handbook: Properties and Selection, Nonferrous Alloys and Special-Purpose Materials 2, 1990, 897-902.
• [4] T.W. Duerig, A.R. Pelton, Ti-Ni Shape Memory Alloys, Materials Properties Handbook, Titanium Alloys 2, 1994, 1035-1048.
• [5] K. Nurveren, A. Akdoğan, W.M. Huang, Evolution of transformation characteristics with heating/cooling rate in Ni-Ti shape memory alloys, Journal of Materials Processing Technology 196 (2008) 129-134.
• [6] M.E. Mitwally, M. Farag, Effect of cold work and annealing on the structure and characteristics of Ni-Ti alloy, Materials Science and Engineering A 519 (2009) 155-166.
• [7] J. Uchil, K.P. Mohanchandra, K.K. Mahesh, K. Ganesh Kumara, Thermal and Electrical Characterization of R-Phase Dependence on Heat Treat Temperature in Nitinol, Physica B: Condensed Matter 253/1-2 (1998) 83-89.