| Issue |
ESOMAT 2009
2009
|
|
|---|---|---|
| Article Number | 02030 | |
| Number of page(s) | 7 | |
| Section | Principles, Simulations, Materials: Background | |
| DOI | https://doi.org/10.1051/esomat/200902030 | |
| Published online | 01 September 2009 | |
DOI: 10.1051/esomat/200902030
In-situ TEM cooling/heating experiments on deformed NiTi shape memory single crystals
T. Simon1, A. Kröger1, Ch. Somsen1, A. Dlouhy2 and G. Eggeler11 Ruhr-University Bochum, Institute for Materials, 44780 Bochum, Germany
2 Institue of Physics of Materials, ASCR, Ziskova 22, 61662 Brno, Czech Republic
Tobias.Simon@rub.de
Published online: 1 September 2009
Abstract
In the present study we report about the influence of dislocations on martensitic transformations in NiTi single crystals. Microstructural investigations are performed on Ni50.4Ti49.6 (at.%) single crystals using in-situ cooling and heating transmission electron microscopy (TEM). Solution heat-treated Ni50.4Ti49.6 single crystals were oriented by electron backscatter diffraction (EBSD) and compressed in [111] B2-direction to different strain levels. DSC measurements on undeformed and deformed material states reveal a two step transformation from B2 to R-phase and then from R-phase to B19´ confirmed by TEM. The analysis of the dislocation structure of a 3.3% compressed single crystal shows that mainly screw dislocations with [001] type burgers vectors are present. During cooling, the martensitic R-phase grows homogeneously. On further cooling in some regions a burst like growth of B19'-neddles can be observed in addition to B19'-regions that nucleate and grow promoted by the stress-fields of dislocations. Dislocation analysis after back transformation suggests that dislocations form as a result of the martensitic transformation.
© Owned by the authors, published by EDP Sciences 2009