Metal flow in porthole die extrusion of aluminium

An understanding of the metal flow in porthole die extrusion is important, because this is reflected in die design and consequently leads to high-performance extrusion. The experimental method to quantify the deformation behaviour for three-dimensional deformation has not been established yet. In this study, an extrusion billet has been devised to investigate the metal flow visibly and quantitatively. The billet was composed of six rings into which thin AA1100 alloy wires were inserted along the extrusion direction. Six rings were made of two kinds of aluminium alloys, AA1050 and AA1100, and they were assembled alternately. The billet to billet extrusion method was employed under conditions of non-lubrication and billet temperature of 723 K. After extrusion, several transverse sections of the extrusion residue were examined. For each transverse section, we examine the following items: the boundary between the first billet and the second billet, the boundaries of each ring and the positions of wires. Through this study, we could figure out which part of the billet flowed into the die exit and the welding plane in the steady-state extrusion. In addition, flow lines were obtained. Furthermore, it was verified that no billet surface flowed into the welding plane in the steady-state extrusion.