MICROSTRUCTURAL CHARACTERISTICS AND DEFORMATION PROPERTIES IN SUPERPLASTIC INTERMETALLICS

Superplasticity in intermetallic alloys is reviewed. Intermetallics wh ich have been demonstrated to be superplastic include nickel-based (Ni 3Al, 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 characteristi cs and deformation properties of superplastic intermetallics are in ma ny ways similar to those observed in conventional superplastic metal a lloys. In the present paper, some of the unusual microstructural featu res pertinent to superplastic intermetallics are described. Two intere sting features are especially highlighted: intermetallics can exhibit superplastic properties in a relatively coarse-grained condition (>100 mu m); and intermetallics with a metastable, inhomogeneous microstruc ture can exhibit superplasticity at low temperatures. Examples are giv en for both cases. In addition, the superplastic deformation mechanism s as well as microstructural characteristics in different intermetalli cs are discussed. (C) 1997 Elsevier Science S.A.