J. Phys. IV France
Volume 112, October 2003
Page(s) 819 - 822

J. Phys. IV France
112 (2003) 819
DOI: 10.1051/jp4:20031007

Structure and properties of severely deformed Ti-Ni-based shape memory alloys

I.Yu. Khmelevskaya1, S.D. Prokoshkin1, S.V. Dobatkin1 and V.V. Stolyarov2

1  Moscow Steel and Alloys Institute, Laboratory of Thermomechanical Treatment, Leninsky Pr. 4, Moscow 1199049, Russia
2  Institute of Physics of Prospective Materials, Ufa, Russia

Structure formation and functional properties of Ti-50.0, Ti-50.7 at. % Ni and Ti-47%Ni-3%Fe shape memory alloys were studied after severe plastic deformation by torsion under pressure (TUP) at RT and equalchannel angular pressing (ECAP) at 400-500  $^{\circ}$C. Nanocrystalline or submicrocrystalline structures were obtained using TUP as a result of deformation ( $\epsilon=5.75$), directly or during post-deformation heating. In alloys having initial martensitic structure, amorphized structure having atomic coordination on the base of B2-austenite lattice forms as a result of the deformation. During further heating at 400-450  $^{\circ}$C, amorphized structure crystallizes in a nanocrystalline austenite structure. In alloys having initial austenitic structure, nanocrystalline austenite structure forms as a result of deformation. During further heating it coarsens and transforms to a submicrocrystalline structure at 450  $^{\circ}$C. As a result of ECAP of Ti - 50.0%Ni alloy in 12 passes at 500  $^{\circ}$C and 8 passes at 400  $^{\circ}$C, a submicrocrystalline structure forms. It provides shape recovery properties comparable to the ones obtained by polygonizing annealing after cold deformation.

© EDP Sciences 2003