Study of the recrystallization behaviour of the aluminium 1565ch alloy during hot rolling of the as cast structures

Abstract

The recrystallization process in 1565 ch aluminium alloy samples was studied in this paper. Existing and well-studied AA5182 aluminium alloy was also investigated for comparison. Samples of both alloys were cut from pre-homogenized ingots and rolled in different modes. After rolling the samples were annealed at different temperatures and the resulting microstructure was studied using scanning electron microscopy and optical microscopy, as well as EBSD (Electron backscatter diffraction) analysis. The study revealed significant differences in the recrystallization processes of these two alloys. Signs of the recrystallization onset without grain growth process can be observed at 10% deformation in 1565 ch alloy. At the same time signs of recrystallization in AA5182 can been observed only when the degree of deformation is over 30%, but the process itself is much faster. 5182 alloy fully recrystallizes after all hot rolling schedules, except for those with 10% deformation. In such case recrystallization timing as a function of Zener-Hollomon parameter and prior strain level ranges from a few seconds to half an hour. In major cases 1565 ch alloy has partially recrystallized structure, which takes 10 to 95 volume %. Exception is the schedule with deformation 50% and Zener parameter 1.77 × 1015, where full recrystallization occurs. With such strain parameters 1565 alloy grain size reaches 6–14 μm. At the same time similar processing provides larger grain size in 5182 alloy, it reaches 10–20 μm. Substructure review immediately after deformation demonstrated, that cellular polygonised structure forms faster in 1565 ch alloy, which can be explained by higher magnesium content. In both cases PSN nucleation mechanism prevails. However, other grain nucleation mechanisms can be observed in 5182 alloy. The main reasons for the abovementioned phenomenon are different magnesium contents and volumes of fine secondary phases.