High temperature deformation of a twin-roll cast AlMg3 alloy

The high temperature plastic deformation of twin-roll cast AlMg3 (AA5754) sheets was investigated. The maximum value of the strain rate sensitivity parameter m = 0.4 suggests superplastic behaviour. However, the maximum ductility of 135% remains below the bottom limit of superplasticity. The investigation of the surface of strained samples using light microscopy and AFM revealed grain boundary sliding at conditions corresponding to the maximum m and dislocation slip in the grain interiors at conditions corresponding to low values of m.