Abstract
Plastic deformation of magnesium alloy AZ91 was investigated at various strain rates in the interval from 3x10^-5 to 1x10^-2 s^-1 and temperature of 420 °C. Samples exhibiting superplastic behaviour were prepared by the three different thermo-mechanical treatments. Microstructure of samples was observed by the light microscopy. Strain rate sensitivity parameter m has been estimated by the abrupt strain rate change method. Possible physical mechanisms of the superplastic flow are discussed.

Key words
magnesium alloy, superplastic flow, dynamic recrystallization, grain boundary sliding, cavitation

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