Local crystal structure of TiNiCu shape memory alloys

Abstract

The features of long-range crystal structure and local environment of Ni and Cu atoms in shape memory alloy Ti50Ni25Cu25 are investigated using X-ray diffraction and extended X-ray absorption fine structure spectroscopy (EXAFS) in the temperature range of direct and reverse martensitic transformations. According to XRD study, alloy has the B2 type structure in austenitic phase and B19 type structure (space group Pmmb) in martensitic phase. EXAFS demonstrates the difference between Cu-Ti and Ni-Ti bond lengths ~ 0.09 Å not typical for common TiNi lattice. The static disordering is more significant in the local environment of Ni atoms than in local environment of Cu atoms.