Microstructural characteristics and deformation properties in superplastic intermetallics

Superplasticity in intermetallic alloys is reviewed. Intermetallics which have been demonstrated to be superplastic include nickel-based (Ni3Al, Ni3Si), iron-based (Fe3Al, FeAl), and titanium-based (Ti3Al, TiAl) alloys. Superplasticity has been recorded in both quasi-single-phase and two-phase intermetallic alloys. The microstructural characteristics and deformation properties of superplastic intermetallics are in many ways similar to those observed in conventional superplastic metal alloys. In the present paper, some of the unusual microstructural features pertinent to superplastic intermetallics are described. Two interesting features are especially highlighted: intermetallics can exhibit superplastic properties in a relatively coarse-grained condition (>100 mu m); and intermetallics with a metastable, inhomogeneous microstructure can exhibit superplasticity at low temperatures. Examples are given for both cases. In addition, the superplastic deformation mechanisms as well as microstructural characteristics in different intermetallics are discussed. (C) 1997 Elsevier Science S.A.