Observations of grain boundary structure in α-Ti

Abstract

Interfacial structure can make very important contributions to the mechanical and physical properties of polycrystalline metals. This has been recognized for many years, and the structure of grain boundaries has been studied extensively in cubic metals over the past several years by means of high resolution transmission electron microscopy (HRTEM) as well as atomic computer simulations. Although hexagonal close-packed (hcp) metals also hold a very important role in metal materials, unfortunately, there have been relatively few experimental investigations of the grain boundaries in hcp metals at the atomic scale. Thus in this particular field, electron diffraction contrast images and computer simulations have always been the dominant methods (4,5,6). The geometrical analysis seems to be more complicated for hexagonal materials than for cubic materials because the formation of three dimensional CSLs (Coincidence Site Lattices) is generally forbidden where the square of the axial ratio is an irrational fraction. The authors address this issue in the present work by presenting results of HRTEM investigations of grain boundaries in [alpha]-Ti, which will provide experimental evidence for theoretical calculations and computer simulations of the grain boundary structure in [alpha]-Ti.