Phase equilibria in the pseudobinary Ti0.5Ni0.5-Ti0.5Cu0.5 system

• The pseudobinary Ti0.5Ni0.5-Ti0.5Cu0.5 system was analyzed using thermodynamic models for the Gibbs energy of individual phases in the system. The TiNi intermetallic phase crystallizes with the B2 CsCl-type structure and is an ordered form of the A2 BCC structure, It was treated with a two-sublattice model (Cu, Ni, Ti, Va)(0.5)(Cu, Ni, Ti, Va)(0.5), where Va represents a vacancy and one sublattice is occupied predominantly by Ti and the other by Ni and Cu. Other phases such as B11 based on a TiCu compound and low-temperature phases B19' and B19 were also described with two-sublattice models with different distribution of atoms on each sublattice, A thermodynamic description of the Ti0.5Ni0.5-Ti0.5Cu0.5 system was obtained from an optimization based on experimental information. The calculated diagram of the pseudobinary Ti0.5Ni0.5-Ti0.5Cu0.5 system at high temperatures exhibits eutectic solidification of liquid and shows satisfactory agreement with experimental data. The phase relations among the B2, B19', and B19 phases at low temperatures mere also assessed on the basis of experimental information from martensitic transformations.

Nyckelord

shape memory characteristics

ni-cu alloys

martensitic-transformation

ti

deformation

model

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