J. Phys. IV France 112 (2003) 819
Structure and properties of severely deformed Ti-Ni-based shape memory alloysI.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 C. Nanocrystalline or submicrocrystalline structures were obtained using TUP as a result of deformation ( ), 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 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 C. As a result of ECAP of Ti - 50.0%Ni alloy in 12 passes at 500 C and 8 passes at 400 C, a submicrocrystalline structure forms. It provides shape recovery properties comparable to the ones obtained by polygonizing annealing after cold deformation.
© EDP Sciences 2003