DUCTILITY AND TOUGHNESS IN INTERMETALLICS

Limited ductility and toughness at low temperatures are serious disadv antages in intermetallics. As in other metallic materials, the two maj or brittle failure modes in intermetallics are cleavage and intergranu lar fracture. We focus on cleavage fracture and the corresponding brit tle-to-ductile transition mechanism. To prevent cracking, a 'sufficien t number' of dislocations must be generated at a crack tip, and this ' sufficient number' appears to be very large. This event is more like a phase transition than an ordinary thermally activated process. In thi s paper a new theoretical model, proposed to explain the BDT is summar ized. The microstructural implications of this model are presented and the means of achieving an acceptable combination of strength and toug hness through microstructural control are then discussed, along with e xamples. (C) 1998 Published by Elsevier Science Limited. All rights re served.