CONTROLLING EMBRITTLEMENT AT GRAIN BOUNDARIES IN INTERMETALLIC COMPOUNDS

Abstract
The present paper first presents some characteristics of structure and electronic (bond) nature for the grain boundary brittleness of the intermetallic compounds. Next, the phenomenological aspects for the grain boundary brittleness of the L1₂-type intermetallic compounds are reviewed with respect to the combination of the constituent atoms, the alloying effect, the stoichiometry effect, and the role of impurity or gaseous atoms. It is emphasized that the brittleness of grain boundaries in the intermetallic compounds are intimately related to the atomistic and electronic structures at grain boundary regions. Based on these systematic observations, it is suggested that the brittleness of the L1₂-type intermetallic compounds can be manipulated by appropriate control of composition and the corresponding electrochemical bond environment at grain boundary planes, and by control of the test environment. Finally, some instances pointing to the materials development are described.