THE AGING EFFECTS IN NiTi SHAPE MEMORY ALLOY WIRE | ||||
The International Conference on Applied Mechanics and Mechanical Engineering | ||||
Article 32, Volume 18, 18th International Conference on Applied Mechanics and Mechanical Engineering., April 2018, Page 1-8 PDF (499.67 K) | ||||
Document Type: Original Article | ||||
DOI: 10.21608/amme.2018.34970 | ||||
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Authors | ||||
I. Özkul1; V. Sampath2; C. A. Canbay3; M. ElFawkhry4 | ||||
1Department of Mechanical Engineering, Faculty of Engineering, Mersin University, Mersin, Turkey. | ||||
2Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai-600 036, India. | ||||
3Department of Physics, Faculty of Science, Firat University, Elazig, Turkey. | ||||
4Central Metallurgical Research Laboratory, Cairo, Egypt. | ||||
Abstract | ||||
ABSTRACT Shape memory alloys occupy a niche position in the domain of advanced materials that have great relevance to medical, engineering, commercial as well as miscellaneous applications. The transformation temperatures of the alloys are immensely important since they decide the specific applications of the alloys in a field. These temperatures are influenced by a host of factors, including composition and thermo-mechanical history of the alloy. In fact, due to continued usage also the transformation temperatures are shifted due to what is known as functional fatigue, which is caused by the build-up of defects within the alloys during use. The horizon of usage of shape memory alloys is ever widening. In the present study, therefore, the effects of aging on the transformation temperatures of NiTi alloys are explored. The martensitic transformation temperatures of the alloys were measured by differential scanning calorimetry, while their microstructures were investigated by optical microscopy. The results show that the aging temperatures as well as the holding times influence the microstructure, which directly affects the transformation temperatures. Aging at high temperature induces precipitation, leading to an increase in the Ti content of the matrix. This in turn caused an increase in the transformation temperatures. On the other hand, aging at low temperature caused stress relief leading to a shift in the transformation temperatures. | ||||
Keywords | ||||
NiTi; DSC; XRD; aging | ||||
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