GRAIN-BOUNDARY CHEMISTRY AND REACTIONS IN METALS

This article has discussed the changes in composition that can occur at grain boundaries in metals and has pointed out how these changes can control the properties of a metal. These changes are most commonly caused either by segregation of an element from the bulk to the grain boundary or as a result of precipitation reactions that occur at the grain boundary. Boundaries are favored sites for such chemical changes because their structure differs from that of the bulk both in the sizes of atoms that can be accommodated there and in the orientations of chemical bonds that can be formed there. As a result of these compositional changes, the chemical bonds at the grain boundaries are different from those in the bulk. It is this change in the chemical bonds at the grain boundaries that make the boundaries’ properties different from those of the bulk. © 1990, Materials Research Society. All rights reserved.