Three dimensional Near-Coincidence Site Lattice modeling of α/β interface boundary structure in two phase titanium alloy

Abstract

In order to study the interface boundary structure, a Near-Coincidence Site Lattice (NCS) theory based on Coincidence Site Lattice (CSL) has been proposed. In this method, coincidence atoms are calculated by a computer based, the atomic matching procedure. The NCS analysis has applied to BCC/HCP systems in three-dimensions to predict results of TEM observation in a Ti-22V-4Al alloy. As the results of HRTEM observation of an α precipitate in β grain, an α precipitate has a lath shape: a broad face boundary consist of misfit dislocations whose spacing is irregularly, while, a side facet boundary are made of regular structure ledges. The NCS analysis is able to predict the α/β interface boundary structure using lattice parameter and orientation relationship between α precipitate and β matrix, and shows good correspondence with the experimental results of side facet obtained by HRTEM observations. Therefore, it is suggested that atomic matching affects strongly the low energy interface boundary structures and the NCS analysis is a useful method to predict the structure of interface boundary. © 2000 ISIJ.