Effect of Extrusion and Annealing Treatment on Peripheral Coarse Grain Structure and Mechanical Property of an Al-Cu-Li-Mg Alloy Extrusion Profile

In the current study, the effects of extrusion and annealing treatment on the peripheral coarse grain (PCG) structure were investigated. The results showed that the edge of profiles recrystallized during the extrusion process, the grain size was in the range of 2-5 m and the degree of recrystallization had obvious heterogeneity along the extrusion direction, showing two kinds of recrystallization microstructure. The thickness of recrystallized microstructure at the head of the profile was 2 mm and there were obvious boundaries. The thickness of recrystallized microstructure at the tail reached 13 mm and there was no obvious boundary. The recrystallized grains grew abnormally to form PCG structure during the solution process. The PCG structure was significantly reduced when the extrusion ratio decreased from 20 to 14. The higher the extrusion temperature reached, the more serious the PCG structure was. The suitable annealing regime is 350°C/5h.