The Requirements for Superplasticity with an Emphasis on Magnesium Alloys

Superplasticity is defined formally as a tensile elongation of at least 400% and a strain rate sensitivity of ≈0.5. It is now well established that superplasticity occurs only in materials having very small grain sizes, typically less than ≈10 μm. These small grains may be achieved in two different ways in magnesium alloys: either by thermomechanical processing or through the occurrence of recrystallization in the early stages of deformation in alloys tested with coarse grain sizes.