MICROSTRUCTURE OF AN EN - AW 6082 ALUMINUM ALLOY PROCESSED BY ASYMMETRIC ROLLING

The possibility of refining the grain structure of commercial Al-Mg-Si alloys was evaluated using the asymmetric rolling technique in the severe plastic deformation (SPD) regime. Bars of annealed alloy having a thickness of 10 mm were rolled at room temperature down to a thickness of 0,2 mm with a laboratory rolling mill featuring the possibility of independently modifying the rotational speed of its two rolls. Trials were performed with speed ratio ranging from 1 (conventional rolling) to 2 (the upper roll rotates at a speed that is twice as that of the lower roll). Analyses on the severely deformed samples were mainly focused on the distribution of hardness and the evolution of microstructure along their thickness as a function of rolling conditions. Experimental tests were carried out by optical and transmission electron microscopy (TEM) and hardness microindentations. The investigation demonstrated that asymmetric rolling can readily promote the achievement Of an ultrafine grained structure (UFG) in the Al-Mg-Si alloy with an improved homogeneity of hardness and microstructure along thickness. This rolling technique therefore represents a promising route for the production of UFG long products such as strips, plates and bars in continuous industrial processing plants.