A Viscoplastic Simulation of Texture Evolution during Extrusion of an Aluminium Alloy

Abstract

Numerical simulations of texture development have been carried out for hot plane strain extrusion of an aluminium alloy using both finite element calculations and a polycrystal plasticity model. The latter is based on the Taylor localisation hypothesis (relaxed constraints) and a viscoplastic constitutive law. We have considered the {111} slip systems and the {100}, {110} and {112} non-octahedral systems. The finite element code first simulates the local extrusion strain paths of the material flow through the die. Secondly, for the different deformation paths between the centre section and the surface the polycrystalline model is used to calculate the local deformation texture evolution. The results are compared with experimentally measured deformation textures at different depths of an extruded bar of a 6082 aluminium alloy. Near the centre section both the numerical simulations and the experimental textures are in good agreement, with typical β-fibre hot rolling texture components as a consequence of the essentially plane strain compression deformation mode. Texture simulations using the non-compact slip systems give significantly better agreement than for slip restricted to the {111} planes. However, very near the surface where there is a very high shear component, none of the models gives good quantitative predictions although there is a reasonable qualitative agreement assuming non-octahedral slip.