EFFECT OF Ti–Al INTERFACIAL ORIENTATION AND Ti DEFORMATION ON THE INTERDIFFUSION RATE AT TEMPERATURES ABOVE THE MELTING POINT OF Al: A MOLECULAR DYNAMICS STUDY

10.25712/ASTU.1811-1416.2022.02.006

Abstract

The influence of the orientation of Ti–Al interphase boundary on the intensity of mutual diffusion, as well as the influence of its deformation of Ti at temperatures above the melting temperature of Al, were studied by the method of molecular dynamics. Zope and Mishin EAM potentials were used to describe interatomic interactions in the Ti–Al system. Three orientations of the boundary relative to the hcp Ti crystal were considered: (0001),  and . It was found that the orientation of the interfacial boundary affects the intensity of diffusion in the Ti phase: Al atoms diffused more intensively into the titanium lattice at the (0001) orientation, and less intensively at the  and  orientations. This influence of the orientation of the interphase boundary is associated with the probability of detachment of the Ti atom from the crystal-liquid interface and is determined by the difference in the energies of the Ti atoms in the aluminium phase and those built into the boundary of the crystalline phase. At the initial stage of mutual diffusion, the boundary between the crystal and liquid metal was observed to shift from the very interface between Ti and Al by two or three atomic planes into the aluminium phase – a thin layer of aluminium near the boundary remained in the crystalline state, repeating the crystal lattice of titanium. This is due to the fact that the Ti–Al bonds at the boundary are much stronger than the interatomic bonds in liquid aluminium. When studying the effect of elastic deformation on the intensity of mutual diffusion, it was found that in almost all cases the intensity of diffusion increases with tension and decreases with compression, which is associated with a corresponding change in the free volume, which largely affects the diffusion mobility of atoms.