Grain-boundary dissociation by the emission of stacking faults.

A range of {l_angle}110{r_angle} symmetric tilt grain boundaries (GB{close_quote}s) are investigated in several fcc metals with simulations and high-resolution electron microscopy. Boundaries with tilt angles between 50.5{degree} and 109.5{degree} dissociate into two boundaries 0.6 to 1.1 nm apart. The dissociation takes place by the emission of stacking faults from one boundary that are terminated by Shockley partials at a second boundary. This is a general mode of GB relaxation for low stacking fault energy metals. The reasons for the occurrence of this relaxation mode are discussed using the theory of GB dislocations. {copyright} {ital 1996 The American Physical Society.}