The effect of magnesium content on the transition process of dynamic restoration during hot deformation of aluminum alloys was investigated. The hot workability of Al-Mg casting alloys were estimated by the observation of the deformation stress, ductlity and deformation structure in hot torsion tests. These tests were conducted on pure aluminum and Al-Mg alloys under the conditions of a strain rate range of 1.45 × 10^-3 to 2.54 × 10^-1sec^-1 and temperature range of 300 to 600°C.
The dynamic restoration process was two folds; for pure aluminum, the dynamic restoration was always by dynamic recovery; but the dynamic restoration in Al-Mg alloys were changed dynamic recovery to dynamic recrystallization which were controlled by magnesium contents and deformation condition (strain rate and temperature).
The ductility of Al-Mg alloys at high temperature deformation was dependent on the dynamically recrystallized grain size. The grain size increased with increasing magnesium content and decreased with the increase of Z factor.