THE PHYSICS OF SUPERPLASTIC DEFORMATION

Superplasticity is an important mode of deformation in metallic alloys with very small grain sizes (usually less than 10-mu-m). In general, high elongations are observed over a rather limited range of intermediate strain rates and there is a decrease in the superplastic effect at both high and low strain rates. The major experimental observations in superplastic metals are summarized and the physical mechanisms of flow are discussed with reference to the behavior at high, intermediate and low strain rates, respectively. Superplastic-like behavior has been reported recently in some ceramics but the experimental evidence suggests that the mechanism of flow in these materials is not the same as in metals.