Effect of twin-roll casting parameters on microstructure and mechanical properties of AA5083-H321 sheet

Abstract

The purpose of the present paper is to study the mechanical properties and microstructure of the twin-roll cast and cold rolled AA5083 aluminum alloy sheet in strain-hardened H321 temper. To reach this goal, first, a sound surface slab of 8.90 mm thick and 1260 mm wide was cast by a 15° tilt back twin roll caster at a casting speed of 490 mm/min. After homogenization at 520 °C, the product was cold rolled to two thicknesses of 6.30 mm and 3.85 mm with an intermediate annealing at 370 °C and final stabilization at 180 °C. Optical microscopy and scanning electron microscopy (SEM) investigations of the as-cast state depicted the segregation of intermetallic particles mainly in grain boundaries which was the cause of grain removal observed in the fracture surface of tensile test samples. In addition, mechanical properties indicated an increase in total elongation after homogenization heat treatment due to the elimination of the grain boundary segregations. Finally, it was observed that the properties of the 3.85 mm thick sheet were consistent with the H321 temper requirements according to ASTM B 290M standard due to applying sufficient cold reduction during cold rolling stage.