Effect of die bearing geometry on flow patterns and thermomechanical history during the aluminum
extrusion process
*Y. Mahmoodkhani1 and M.A. Wells1, N. Parson2
1
University of Waterloo
200 University Ave W, Waterloo ON, Canada N2L 1V9
(*Corresponding author: y3mahmoo@uwaterloo.ca)
2
Rio Tinto, Arvida Research and Development Centre
P.O. Box 1250, Jonquière (QC) G7S 4K8
ABSTRACT
It is well known that the extrusion die bearing geometry can influence the material flow and deformation
conditions experienced from surface to centre of extrusions. The formation of Peripheral Coarse Grains
(PCG) near the surface of medium strength aluminum extrusions is thought to be related to this variation in
deformation conditions and can be detrimental to in-situ extrusion performance. In this research, a
combination of experimental and computer modeling techniques were used to understand the effect of die
bearing geometry on the deformation conditions experienced through the thickness of a AA3003 extrusion.
Extrusion trials was performed at 450°C using four different dies with different bearing geometries
including; no-bearing (zero bearing), 25 mm flat, 35 mm choked and curved bearing (Controlled Strain
Rate). The extrusion was interrupted in the middle and the remaining billet inside the container was
removed and quenched to maintain the as-deformed structure. Optical metallography was used to observe
and characterize the as-deformed grain structure to understand the effect of the bearing die geometry on
material flow patterns and grain deformation inside the container and bearing zone during extrusion. To
obtain a more quantitative understanding of the effect of die bearing geometry on surface to centre
deformation conditions, a mathematical model of the extrusion process was performed with a validated
FEM model developed using DEFORM-2D.