Dilatometric study of SME and TWSME in TiNi alloy

Abstract
TWSME and SME, the B2-phase aging and B19'-martensite texture have been studied by methods of dilatometry, TEM and X-ray in Ti-50.5 at.% Ni alloy after rolling in austenitic state and after tension. TWSME of austenitic type takes place after rolling and after tension at 623 K. TWSME of martensitic type takes place after tension at room temperature. We showed that Ti ₃Ni ₄ particles precipitated in Ti-50.5 at.% Ni alloy at 623 K, and they dissolve at 773 K. This precipitation increased martensitic transformation temperatures and deformation of TWSME. Dissolving of particles decreased transformation temperatures and deformation of TWSME. The increase of TWSME deformation during precipitation is due to oriented arrangement of particles relatively to deformation and oriented nucleation of martensite on particles. After tension at room temperature specimens contain B19'- martensite with axial texture [001] and have negative thermal expansion coefficient to this direction. We showed that (020) and (111) interplanar spacings of B19'-phase decreased, but (002) and (111) interplanar spacings increased with temperature decrease.