The crystallography and deformation modes of hexagonal close-packed metals

The extensive data on the metallography and crystallography of face-centred cubic and body-centred cubic metals have been the subject of several reviews in recent years, but in comparison the data for hexagonal close-packed metals remain dispersed in the literature. This is unfortunate, since the h.c.p. structure presents a number of confusing features not encountered in cubic structures. With the increasing technological application of h.c.p. metals, there does appear to be a need for a summary of the structure of these metals, with particular emphasis on the fundamentals of plastic deformation. It was considered appropriate in this review to mention electron diffraction and dislocation image contrast in thin foils of hexagonal metals, as future research on these materials will undoubtedly make use of the transmission electronmicroscopy technique.