Solution effect on improved structural compatibility of NiTi-based alloys by systematic first-principles calculations

The functional stability of a shape memory alloy (SMA) may be related to its structural compatibility between the parent-phase and the martensitic-phase structures. In this study, we perform systematic first-principles calculations for 276 Ni-Ti-based ternary alloys to investigate their energetic stability as well as their structural compatibility between the parent- and the martensitic-phase structures. We analyze in detail the dependences of the energetics and structural properties on the additional element X, on X concentration, and on the replaced chemical element. Some X are found to energetically stabilize the B19 structures more than the B19' structures at X concentrations above 6.25 at. %. It is also found that the B19-B2 martensitic transformation shows better structural compatibility than the B19'-B2 transformation for most of the investigated ternary Ni-Ti-X alloys. These alloys also tend to have better structural compatibility than binary equiatomic NiTi. Moreover, we screen the investigated alloys on the basis of their energetic stability and structural compatibility, and we identify 26 Ni-Ti-X alloys as possible SMAs with good functional stability. In this study, we reveal a strong potential of the computational design for improving the functional stability of Ni-Ti SMAs by alloying additional elements.