The production of high quality powder metallurgical NiTi alloys with elevated phase transformation temperatures is challenging. During processing, an unavoidable pickup of impurity elements (especially oxygen and carbon) results in a decrease of phase transition temperatures and in the formation of
Evolution of transformation characteristics with heating/cooling rate in NiTi shape memory alloys
✍ Scribed by K. Nurveren; A. Akdoğan; W.M. Huang
- Publisher
- Elsevier Science
- Year
- 2008
- Tongue
- English
- Weight
- 841 KB
- Volume
- 196
- Category
- Article
- ISSN
- 0924-0136
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✦ Synopsis
The martensitic transformation behavior, morphology and transition temperatures in NiTi-based shape memory alloys (SMAs) are strongly influenced by thermo-mechanical treatments. The present work aims to study the influence of heating/cooling rate on the transformation characteristics of a near-equiatomic NiTi SMA. There is a critical annealing temperature range where the transformation characteristics measured in the NiTi SMA are remarkably different. The changes in the transformation characteristics at different heating/cooling rates were studied by means of differential scanning calorimeter (DSC) measurements for four NiTi SMAs, which were made of the same raw material but heat-treated below and above the critical temperature. The results showed that the heating/cooling rate has strong influence on the transformation temperatures, the absorbed/released heat, and the elastic and irreversible energies during transformation.
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