Linking plane strain compression tests on AA6063 to laboratory scale extrusion via constitutive equations

Modelling aluminium extrusion is complex since mechanical behaviour of the material is dependent on temperature, strain path, initial microstructure and microstructure developed. These dependencies are incorporated in so-called constitutive equations and a simple method to determine them is by using plane strain compression (PSC) tests. In order to assess the potential of using these constitutive equations for extrusion modelling, an AA6063 alloy was studied. Plane strain compression tests were carried out with a Gleeble thermomechanical simulator at varying temperatures and for varying homogenisation treatments, which involve different solute Mg and Si contents in the matrix. Flow stress was recorded as a function of strain and the constitutive data were modelled using a modified hyperbolic sine law, which explicitly accounts for the effect of solute Mg and Si. Extrusion experiments were carried out with a laboratory extrusion press using a simple die geometry. Extrusion was performed at low speed and controlled such that isothermal conditions prevailed. Temperature and homogenisation treatments were identical to those of the PSC tests. A linear relation between the flow stress during PSC testing and extrusion pressure was obtained.