Chemistry and bonding changes associated with the segregation of Bi to grain boundaries in Cu

Grain-boundary embrittlement, caused by the segregation of impurity and alloying elements, occurs in many systems and has been the focus of a large amount of research owing to its technological importance. However, the exact mechanism by which the segregating elements cause embrittlement remains unclear. In this paper the localized changes in the electronic structure in the classical embrittling system of Bi in Cu have been studied. Experimental results were obtained by examining the fine structure in the electron energy loss spectrum which was then compared to calculations using the layer Korringa-Kohn-Rostoker (LKKR) method. A change in the d density of states has been observed for the Cu atoms at the grain boundary, associated with Bi, and an electronic model to explain embrittlement is described.