Microstructure evolution, plastic anisotropy, and intergranular corrosion of Al-Mg-Si sheet processed through a combination of hot extrusion and cold rolling

Abstract

Peak-aged Al-Mg-Si alloys fabricated through a combination of hot extrusion and cold rolling were studied, and the microstructure evolution, mechanical properties, plastic anisotropy, and intergranular corrosion (IGC) were clarified. The results show that fully dynamic recrystallization and grain growth occurred during the hot extrusion, resulting in a coarse and equiaxed grain structure. The cold rolling caused an elongation of the coarse grains and the formation of some fine grains. After solution and aging, the as-extruded grains were unchanged, whereas the as-rolled specimens exhibited a finer grain structure with a large amount of high-angle grain boundaries owing to the occurrence of static recrystallization. All as-extruded/rolled specimens mainly showed a cube and Goss texture. In the peak-aged state, the deformation textures of the rolled specimens decreased to a low level, whereas the fraction of Q and R significantly increased. A fine high-density needle-like β″ phase was uniformly distributed in all aged specimens. If the thickness of the peak-aged Al-Mg-Si sheet is uniform, the combination of hot extrusion and cold rolling, or an increase in the rolling reduction, can enhance the tensile strength and elongation. Although the combined process enhanced the plastic anisotropy, the variation in the r-values along the different directions was decreased. The IGC resistance of the Al sheet experienced hot extrusion and cold rolling, and the peak aging was slightly reduced owing to a high fraction of high-angle grain boundaries.