A PRACTICAL APPROACH TO THE THEORETICAL STRUCTURE OF GRAIN BOUNDARIES

Abstract

This paper surveys the current theoretical models of grain boundary structure and attempts to see to what extent they are capable of defining the boundary structure found in commercial polycrystalline materials. It is shown that an adequate description of the intrinsic dislocation content is achieved by such models but that further classes of defect are to be expected and found in commercial materials. 1 . Introduction. The real structure of grain boundaries is a topic of great theoretical interest and practical importance. Modern metallic-based materials are normally utilized in technological practice in a polyphase polycrystalline form. In such a form the distribution of phases and of defects is of major importance in controlling material properties. To understand the r81e of grain (or crystal) boundaries in determining properties and the influence they have on the development of microstructure during thermomechanical processing, it is essential to develop a clear picture of grain boundary structure. Further, it is necessary to be able to determine at least some aspects of this structure experimentally. This article seeks to look, in outline, at the development of theoretical models of grain boundary structure concentrating on findings that have been subject to experimental verification. The aim is to see to what extent current theoretical models are capable of describing the type of grain boundary structure seen in practical polycrystalline