A comparative study of martensite crystal lattice in nanostructured, quenched and deformed Ti-Ni shape memory alloys

The crystal lattices of cooling-induced (thermal) martensites formed in thermally and thermomechanically treated Ti-Ni Shape Memory Alloys (SMA) and stress-induced, reoriented and plastically deformed martensites were studied using the X-ray diffraction method. The linear dependences of the quenched B19’-martensite lattice parameters (LPs), maximum transformation lattice strain in single- and polycrystalline B2-austenites as well as its crystallographic direction on nickel concentration in the hyperequiatomic range are presented. The lattice parameters and maximum transformation lattice strain of martensite formed from nanocrystalline or polygonized austenites differ from those of quenched martensite formed from recrystallized austenite. The averaged LPs of stress-induced, reoriented and moderately plastically deformed martensites are close to the lattice parameters of quenched martensite