Uniform Equiaxed Grain Structure throughout Thickness of a Hot-Rolled 5083 Al-Mg-Mn Alloy Thick Plate after a Tempering Treatment at 350°C

Abstract

In a conventional hot-rolled 5083 Al-alloy thick plate, the crystalline structure at the central part in the thickness direction comprises primarily slender grains. However, the grain structure is always equiaxed near the surface of the rolling plate. In this experiment, the shape of the slab before hot rolling was changed to a trapezoid. The main goal is to increase the amount of plastic strain and increase the dislocation density in the central part of the plate hot-rolled from the trapezoidal aluminum slab. TEM observations indicated that the center of the plate of hot-rolled trapezoidal slab had a higher dislocation density than the center of the rectangular slab. Subsequent heat treatment caused the treated grains to become equiaxed. Therefore, an equiaxed grain structure that was uniform in the thickness direction of a hot-rolled thick plate could be obtained because the hot rolling of the trapezoidal slab caused profound lateral strain, in addition to extensive deformation in the rolling direction. The excess deformation resulted in a high dislocation density in the central region of the as-hot rolled plate, increasing the strain energy that was stored for recrystallization.