Superplasticity of AlMgSi alloys

Commercial AlMgSi alloy sheets produced by thermomechanical treatment are found to be superplastic between 500 and 570°C at strain rates of 10−5–10−3−1 The strain rate sensitivity,m, is about 0.4. It was found that the highly alloyed sample contains pre-existing cavities in higher volume fraction than the alloy of lower concentration. An exponential growth of cavity volume fraction was found during superplastic deformation which is characteristic of plasticity controlled cavitation. The growth rate of the cavity volume fraction can be decreased by applying back pressure.