Experimental investigation and thermodynamic calculation of the Ti-Ni-Cu shape memory alloys

The effect of Cu content on the thermoelastic martensitic transformation in TiNi shape memory alloys (SMAs) was systematically investigated by means o f differential scanning calorimetry (DSC). Martensitic transformation tempe ratures and transformation enthalpy were measured for a series of alloys wi th composition Ti50Ni50-xCux (x = 0 to 13 at. pet). The measured data were then used to evaluate the thermodynamic properties of the low-temperature o rthorhombic B19 and monoclinic B19' phases using a two-sublattice model (Ni , Cu, Va)(0.5)(Ni, Cu, Ti)(0.5) in combination with the thermodynamic descr iption of the parent B2 phase. The vertical section of the pseudobinary TiN i-TiCu was calculated including the B19 and B19' phases. Transformation ent halpy and stress rate were predicted for the ternary TiNiCu SMAs, which are in reasonable agreement with experimental data.