Multi-objective optimization and experimental investigation on hot extruded plate of high strength Al-Zn-Mg alloy

Abstract

The hot extrusion process of an Al-Zn-Mg plate was studied via numerical and experimental methods. The multi-objective optimization method was employed to optimize the structure of the feeder chamber. Additionally, an extrusion experiment was conducted using the optimal feeder chamber. Based on above analysis, the optimal structure of the feeder chamber was obtained, and the standard deviation of the flow velocity was decreased from 0.827 to 0.499 mm/s. Meanwhile, the die displacement and extrusion load were also reduced significantly. The extruded plate consisted of substructures, elongated grains, and fine grains of several microns, which was evidence of the dynamic recovery and partial dynamic recrystallization. The main textures of the extruded plate were deformed Brass, S, and Copper, as well as some recrystallized Cube. However, the fraction of the aforementioned texture components exhibited significant variation in the center and edge areas of the extruded plate. The center of the plate exhibited higher hardness, lower elongation, and lower ultimate tensile strength than the edge area. Differences in the tensile properties along 0°, 45°, and 90° were observed, indicating the anisotropy of the extruded Al-Zn-Mg plate. Keywords: Hot extrusion, Al-Zn-Mg alloy, Die structure, Optimization, Microstructure