Pre and post rolling homogenization of direct chill cast Al-6Mg alloy: effect on microstructure and mechanical properties

Abstract

ABSTRACT Production of high-Mg content Al–Mg alloys in the form of sheet from cast condition, should be performed with some pre- and post-deforming treatments to achieve desirable mechanical properties. In this research, to find the necessity and influence of pre- and post-rolling homogenisation process on Al–6Mg alloy properties, series of experimental investigations were carried out on direct chill (DC) cast Al–6Mg. Hot extrusion at the temperature of 350°C has been selected as a pre-rolling homogenisation process, which leads to homogenisation by formation of partially recrystallised grains. Cold rolling performed on both DC cast and hot extruded samples up to 80%. Post-rolling homogenisation process done by annealing at 350, 450 and 550°C. Results show that pre-rolling hot extrusion is effective for stability of mechanical properties after cold rolling. Good combination of strength and ductility is achieved for the cold-rolled sample followed by annealing at 450°C. Changes in strength and ductility of the alloy after both pre- and post-rolling homogenisations are controlled by recovery resulting from dislocation arrangement and formation of subgrains. Both pre- and post-rolling homogenisation are effective in improving mechanical properties of cast Al–6Mg, however post-rolling process is more effective if the annealing temperature is chosen correctly.