The deformation of commercial aluminum-magnesium alloys

Abstract

The deformation and fracture of Al-Mg alloys have been investigated over a range of strain rates and temperatures. The rate and temperature-dependence of the deformation can be understood on the basis of the mobility of Mg atoms. When the Mg atoms can diffuse at a sufficient rate they interact with dislocations to produce serrated yielding and a zero or negative strain rate sensitivity. This greatly restricts the tensile ductility. Outside of this serrated flow regime enhanced ductilities are achieved due to the positive strain rate sensitivity stabilizing any inhomogeneities which develop. However, the final fracture is also influenced by the constituent particle concentration. Voiding occurs at particles and if the concentration of particles is sufficiently large the voids link up by local shear. Decreasing the constituent particle concentration, together with a reduction in the amplitude of serrations, results in larger tensile ductilities. At high temperatures, quite large strain rate sensitivities can be achieved but the ductility is finally limited by the propensity for voiding in these alloys.