Ductility and toughness in intermetallics

Limited ductility and toughness at low temperatures are serious disadvantages in intermetallics. As in other metallic materials, the two major brittle failure modes in intermetallics are cleavage and intergranular fracture. We focus on cleavage fracture and the corresponding brittle-to-ductile transition mechanism. To prevent cracking, a 'sufficient 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 this paper a new theoretical model, proposed to explain the BDT is summarized. The microstructural implications of this model are presented and the means of achieving an acceptable combination of strength and toughness through microstructural control are then discussed, along with examples. (C) 1998 Published by Elsevier Science Limited. All rights reserved.