Plastic deformation of extruded AZ91 magnesium alloy was investigated at various strain rates and in a temperature range of 360-420°C. Samples exhibiting superplastic behaviour were prepared with different thermo-mechanical treatments. Microstructure of samples was observed by light and scanning electron microscopy. The strain rate sensitivity parameter m has been estimated by the abrupt strain rate change method. Possible physical mechanisms of the superplastic flow are discussed.
Fine-grained magnesium alloy QE22 (Mg-2.5wt.%Ag-2.5wt.%RE-0.6wt.%Zr) was prepared from cast ingot which was submitted to a two stages heat treatment. Subsequently the billet was overaged and extruded at high temperature. Samples were deformed at elevated temperatures from 380°C up to 480°C at various strain rates. Microstructure of deformed samples was studied using light and electron microscopy. Conditions for superplasticity of the investigated alloys have been estimated. Possible deformation mechanisms are discussed.
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