Influence of compression aging on phase transition temperatures in single crystalline Ni-rich NiTi shape memory alloys
✍ Scribed by J. Michutta; A. Yawny; M. C. Carroll; Ch. Somsen; G. Eggeler
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 313 KB
- Volume
- 35
- Category
- Article
- ISSN
- 0933-5137
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✦ Synopsis
The present paper considers the phase transition behavior of a single crystal Ni-rich NiTi alloy which was compression aged to produce one single family of Ni 4 Ti 3 precipitates.
The single crystal material was produced in a two stage process.
Polycrystalline material was first melted under an inert atmosphere and remelted when single crystals were produced. Compression aging treatments in <111>-orientation were carried out in order to suppress all but one family of Ni 4 Ti 3 -precipitates which nucleate and grow on {111}-planes of the B2 matrix. The objective of this study is to investigate the influence of Ni 4 Ti 3 -precipitates on the martensitic transformation behavior. It was previously shown that grain boundaries provide heterogeneous nucleation sites for the formation of Ni 4 Ti 3 ; this results in heterogeneous microstructures which undergo multiple step martensitic transformations. Single crystals avoid grain boundaries and the present study aims at clarifying how homogeneously precipitated particles affect martensitic transformations.