J. Phys. IV France 11 (2001) Pr8-445-Pr8-449
Microstructure of quenched Ni-rich Ni-Ti shape memory alloysCh. Somsen1, J. Kästner1, E.F. Wassermann1, Ph. Boullay2 and D. Schryvers2
1 Labor für Experimentelle Tieftemperaturphysik, Gerhard Mercator Universität, Lotharstrasse 1, 47057 Duisburg, Germany
2 EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
Microstructural investigations with transmission electron microscopy were carried out on quenched Ni-Ti alloys with 52 and 54.5 at% Ni. For the Ni52Ti48 specimen long time exposed diffraction patterns of a single grain show besides the expected reflections of the B2-phase, two sets of extra reflections in different zones. The first type of spots is explained by lattice displacement waves, which are regarded as precursors of the martensitic Ni-Ti phases, B19' and R-phase, respectively. The second set of reflection with more diffuse intensity than the other reflections is related to Ni4Ti3 precipitates in an early state of formation. For the Ni-richer Ni54.5Ti45.5 alloy only Ni4Ti3 precipitates in an early state of formation are found but no precursors of the B19' - and R-phase.
© EDP Sciences 2001