Abstract
The structures of selected small- and large-angle [001] tilt boundaries in gold bicrystals were studied using X-ray diffraction techniques. All the boundaries examined gave rise to extra reflections. It was shown that these reflections could not result from (1) double diffraction, (2) surface diffraction or (3) diffraction of radiation with one-half or one-third of the characteristic CuKα wavelength and, therefore, must come from the grain boundary. The presence of these reflections is direct evidence for the periodic nature of all the grain boundaries studied. The grain boundary reflections were frequently split into pairs which are present on the high- and low-angle side of the tail of the f.c.c. reflection. This splitting was related to the presence of a small twist component superimposed on the tilt boundary. In general the low-angle reflections were observed to be higher intensity than the high-angle reflections. The analysis of these intensity observations indicates that the tilt-boundary structure in the plane of the boundary consists of a large region with a small expansion followed by a small region with a large contraction. The diffraction technique is unique in being able to obtain this type of detailed information on the structure of grain boundaries.