Simulation of taper heating and variable pressing rate to improve extrusion performance for high-strength aluminum alloys

The main process parameters of direct and indirect extrusion of aluminum alloys were studied using FE-modeling in this article. The subject of the study was the use of billets taper heating and variable pressing rate as compared to the standard extrusion conditions. Extrusion of AA2024 grade alloy and experimental Al-2%Cu-1.5%Mn-1%Mg-1%Zn alloy was considered. The flow stress-on-strain dependences within the 350 degrees C-450 degrees C range at strain rates of 0.1-10 s-1 were determined for the experimental alloy. Considering the time of billet transportation to the extrusion equipment, its optimum temperature gradient was determined to be 500 degrees C at the front end and 140 degrees C at the tail end. Direct extrusion of taper heated billets at the variable rate and elongation of 7 allowed increasing the process performance by 5.6 times (from 1.8 mm s-1 to an average of 10 mm s-1, in case uniformly heated billets are extruded at the constant rate). In case of pressing at high elongations (15 and 25), the performance increase was about 2 times. It was found that the use of taper heating, both in case of grade alloy and model alloy extrusion, in all the considered conditions, allows achieving a significant increase in performance. However, these results are considered to be most effective in case of direct extrusion at small elongation ratios.