Optimization of the extrusion die and microstructure analysis for a hollow aluminum alloy profile

The virtual tryout of the extrusion process of a large hollow aluminum profile is carried out by using numerical simulation. Firstly, a porthole die is designed based on the theory of metal plastic forming, and a finite element model of the extrusion process is established. Following the simulation results, the height and shape of baffle plate are adjusted to balance the material flow velocity in the cross-section of the profile. Through a series of modifications, the standard deviation of the velocity (SDV) at the profile section decreases significantly from 6.1 mm/s that is in the initial state to 3.5 mm/s in the optimum one. Finally, a physical extrusion die is manufactured based on the optimized design, and the extruded profile satisfies the practical requirements. In addition, the microstructure distribution on the product section is analyzed numerically. Results show that the uneven deformation caused by the difference in wall thickness is the main factor that causes the uneven distribution of grain sizes in the cross-section of the product. When the material flows out of the die orifice and undergoes uneven temperature distribution at the profile section, the grain growth rates become different.