Extreme values of elastic moduli and Poisson's ratio of TiFe and TiNi with shape memory

Among the macroscopic characteristics of solids, elastic properties play a crucial role in the analysis of the loss of stability of the crystal lattice of materials to phase transitions. For shear-type transitions, such as martensitic transformations in metals and alloys, the study of the anisotropy of the parameters of crystal structures: elastic moduli and constants, Poisson's ratio, and others is of particular importance. In this paper, the surfaces of Young's and shear moduli of crystals, as well as the Poisson's ratio and their central sections are constructed. Extreme values of the moduli and the Poisson's ratio of the crystals are calculated. Transformation of surfaces and their central sections is given in the context of loss of stability of alloys to martensitic transformations.