The relationship between stress and strain rate is often sigmoidal in superplastic materials, with a low strain rate sensitivity at low and high strain rates (regions I and III, respectively) and a high strain rate sensitivity at intermediate strain rates (region II) where the material exhibits optimal superplasticity This relationship is examined in detail, with reference both to the conflicting results reported for the Zn-22 pct Al eutectoid alloy and to the significance of the three regions of flow

The mechanical properties of superplastic materials

On this seventy-fifth anniversary of the first scientific report of true superplastic flow, it is appropriate both to look back and examine the major developments that established the present understanding of superplasticity and to look to the future to the new opportunities that are made possible by new processing techniques, based on the application of severe plastic deformation, that permit the production of fully dense bulk materials with submicrometer or nanometer grain sizes. This review proposes a minor modification to the present definition of superplasticity, it provides an overview of the current understanding of the flow of superplastic metals and ceramics and then it examines, and gives examples of, the new possibilities that are now available for achieving exceptional superplastic behavior.

Seventy-five years of superplasticity: historic developments and new opportunities

Creep at low stress levels in the superplastic Zn-22% Al eutectoid

The activation energies associated with superplastic flow

The microstructural aspects of the superplastic phenomenon are reviewed. The experimental results of a very large number of investigations are critically analysed in the context of: grain shape and size; grain growth; grain boundary sliding and migration, grain rotation and rearrangement; diffusion and dislocation activity. It is shown, that in spite of often conflicting evidence in the literature, a common pattern of microstructural behaviour emerges for all the materials and conditions investigated to date.

Microstructural aspects of superplasticity

https://escholarship.org/content/qt1q877575/qt1q877575.pdf?t=p21n8t

M.L. Vaidya

Papers

High-temperature deformation mechanisms in superplastig ′n-22Al eutectoid