Martensitic transformation of NiTi nanocrystals embedded in an amorphous matrix
- Institute of Materials Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna (Austria)
The influence of the size on the martensitic phase transformation of spherical NiTi nanocrystals embedded in an amorphous matrix was studied by transmission electron microscopy. The transformation from B2 austenite to B19' martensite is suppressed by a transformation barrier that increases with increasing transformation strains and decreasing diameter of the nanocrystals. Minimizing the strain and interface energy yields a two step transformation from B2 to the R-phase and finally to B19'. The transformation starts at the crystalline/amorphous interface by heterogeneous nucleation. In the case of the R-phase to B19' transformation large strains occur causing after a certain point fine compound twinning during growth that finally leads to a complete transformation right up to the interface. In the isolated nanocrystals a lack of collective transformation effects yields larger transformation barriers and causes larger critical diameters than those observed in the grains of nanocrystalline NiTi.
- OSTI ID:
- 20634800
- Journal Information:
- Acta Materialia, Vol. 52, Issue 19; Other Information: DOI: 10.1016/j.actamat.2004.08.003; PII: S1359-6454(04)00470-7; Copyright (c) 2004 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 1359-6454
- Country of Publication:
- United States
- Language:
- English
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