Accession Number : ADA184808

Title :   Study of Boundary Structures.

Descriptive Note : Final rept. 1 Apr 83-31 Jul 87,

Corporate Author : WASHINGTON UNIV SEATTLE DEPT OF MATERIALS SCIENCE AND ENGINEERING

Personal Author(s) : Kikuchi, Ryoichi

PDF Url : ADA184808

Report Date : 31 Jul 1987

Pagination or Media Count : 17

Abstract : The project extends previous studies on structures of a 2-D grain boundary (g.b.). The basic analytical tool is the cluster variation method (CVM) and the path probability method (PPM), both developed by the author. In the CVM, the free energy is minimized with respect to a large number of variables using a linear iteration method called the natural iteration method (NIM). A square lattice is chosen as the basic lattice (called the DSC lattice) of the analysis. The first, second, and third nearest neighbor pairs are excluded due to a large repulsion. The fourth and fifth neighbors contribute interaction potentials E(4,AB) and E(5,AB), and so on. In the DSC lattice the CVM is formulated using a cluster made of nine lattice points in the form of a quadruple square. The QS formulation leads to numerical results that are reliable compared with the MC method. In low temperatures, atoms hardly deviate from the skeletal stable crystalline structure. The pair method is found to give reliable numerical results practically the same as those of QS for low temperatures including the entire ordered phase in the work D. This result is significant because when the pair method is used, the two sides of the g.b. do not need to be oriented symmetrically as were done in the present report. Applications of this point of view for g.b. of different angle combinations and the 3-D cases are now planned.

Descriptors :   *GRAIN STRUCTURES(METALLURGY), *GRAIN BOUNDARIES, *LATTICE DYNAMICS, VARIATIONAL METHODS, MELTING, LOW TEMPERATURE, TOUGHNESS, STRENGTH(MECHANICS), DIFFUSION, STATISTICAL MECHANICS, ITERATIONS

Subject Categories : Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE