Every, Blackman diagrams, Cauchy pressure and analysis of elastic properties of the crystal lattice of Ti49Ni51 (at. %) and TiNi – TiFe alloys with and without martensitic transformations

In this paper, to analyze the elastic properties of Ti49Ni51 (at. %) and TiNi – TiFe crystals with and without martensitic transformations Every’s and Blackman’s diagrams are used as two ways to characterize the elastic properties of cubic materials. Paired correlations between the parameters (s2, s3), (s3, s1) и (F44, F12) are calculated. The evolution of the Cauchy pressure pC value depending on the content of iron atoms in the crystal lattice of alloys is considered. It is established that, regardless of the composition of the alloys, the Cauchy pressure is greater than zero and decreases almost monotonically from 100.5 to 35.0 GPa with an increase in the content of Fe atoms in the B2 crystal lattice of the TiNi – TiFe phase and an increase in its stability with respect to martensitic transformations (up to complete stabilization). This evolution of pC corresponds to the data according to which a significant component of the bonding forces in TiNi is a metallic bond, and with an increase in the concentration of Fe atoms in alloys instead of Ni atoms and approaching the composition of TiFe, the proportion of the covalent component of the bonding forces increases.