On micro-superplasticity

Micro-superplasticity phenomenon, i.e. formation of thin fibers, whose appearance suggests extremely high strain in the local regions, has been documented in a number of plastically and superplastically deformed materials, predominantly in aluminum alloys. The fiber formation occurs both at the fracture surface and at the deformed surface. The fiber length increases with the total strain, and it is maximum under the optimum superplastic strain rate. An ultra-fine grain structure, a high concentration of oxygen and often high concentration of the alloy elements have been observed in the fibers. Suggested explanations for fiber formation have been reviewed, the important role of oxidation reactions has been emphasized. (C) 1997 Acta Metallurgica Inc.