Estudo da influência dos tratamentos termomecânicos T8 e T851 na microestrutura e no comportamento de corrosão da liga AA2198

Abstract

Al-Cu-Li alloys present advantages in relation to conventional Al-Cu alloys in applications for aerospace industry due to their low density and good mechanical properties. The mechanical properties of these alloys depend on their microstructure and this is affected by the thermomechanical treatments to which the materials are submitted during their fabrication process. In the present study, the effects of T8 and T851 thermomechanical treatments on the corrosion resistance of the AA2198 alloy were compared. The main hardening precipitate in Al-Cu-Li alloys is the T1 phase, (Al2CuLi). The presence of this precipitate in the AA2198-T8 and T851 alloys was analyzed by transmission electron microscopy (TEM). The microstructure of both alloys was evaluated by Vickers micro hardness and differential scanning calorimetric (DSC) measurements and the results obtained were correlated. The results showed higher density of T1 phase for the T851 condition. Besides, microstructural characterization revealed elongated grains for the T8 condition and equiaxed grains for T851 condition. These results were related to the corrosion behavior of both alloys by immersion and gel visualization tests.