Effects of Alloying Additions on Intergranular Fracture of Ordered Intermetallics

Abstract

ABSTRACTThe majority of ordered intermetallics generally exhibit brittle fracture and poor ductility at ambient temperatures, and their brittleness is strongly associated with grain boundary properties. Recent efforts on alloying approaches and microstructural modifications gave promising results to improve the ductility of ordered intermetallics. This article summarizes recent studies on understanding the intergranular brittle fracture from the point of view of compositional and resultant structural (and electro-chemical) properties of grain boundaries. Significant improvement in ductility has been established by the control of chemical composition, that is, by the selection of constituent elements, the control of alloy stoichiometry, the addition of substitutional elements, the change of degree of ordering and the doping by the interstitial elements. Also, the gaseous atoms hydrogen and oxygen from environment or as residue are shown to strongly affect the grain boundary fracture behaviour. Emphasis will be placed on the L12-type ordered intermetallics including Ni3Al, Ni3Si and Co3Ti.