STRUCTURAL-PHASE TRANSFORMATIONS IN HETEROPHASE STRUCTURES OF NICKEL AND TITANIUM ALUMINIDES DURING THEIR SYNTHESIS: MOLECULAR DYNAMICS STUDY OF PHASE FORMATION

10.25712/ASTU.1811-1416.2023.03.001

Abstract

Using the software packages LAMMPS and OVITO, molecular dynamics simulation of the process of self-propagating high-temperature synthesis (SHS) of nickel and titanium aluminides and the study of structural-phase transformations with the formation of heterophase structures during their synthesis were carried out. To describe interatomic interactions in the Ni–Al and Ti–Al systems, the EAM potentials of P. Purja, R. Zope, and Y. Mishin were used. For the Ni–Al and Ti–Al systems, the following two types of initial structures were considered: layered and matrix nanocrystalline composite structures with different component stoichiometry and certain temperature conditions for SHS initiation (ignition). In the study of the kinetics of SH-synthesis of intermetallic compounds of two systems, the conditions for stoichiometry and combustion temperature ranges were established, which distinguish between the manifestations of the following heterogeneous mechanisms of the SHS reaction and structure formation of intermetallic compounds: reactive dissolution, reaction diffusion, crystallization from the melt, and "mosaic" dissolution with the nucleation and growth of nanocrystalline nuclei. For a layered Ni–Al nanocomposite structure with a stoichiometry of Al-79.75 at. % Ni, the kinetics of structural-phase transformations is illustrated in sufficient detail, indicating the identified stacking faults and dislocations. In addition, illustrations of the kinetics of structural-phase transformations are also given for matrix nanocomposite structures of two systems.