Influence of texture and grain structure on strain localisation and formability for AlMgSi alloys

Abstract

Abstract The influence of texture and grain structure on strain localisation and formability is examined by experiments and numerical simulations for the extruded aluminium alloys AA6063 and AA6082. In the as-extruded condition, the AA6063 alloy has an equiaxed, recrystallised grain structure with strong cube texture, while AA6082 has a fibrous, non-recrystallised grain structure with strong β-fibre texture. By deforming and heat treating the materials after extrusion, a recrystallised equiaxed grain structure with a close to random texture is obtained for both alloys. A comprehensive test programme is conducted to determine the work hardening, plastic anisotropy and formability of the materials. Strain localisation and failure are examined by optical microscopy. An anisotropic plasticity model is calibrated for the materials and used in calculation of forming limit curves by means of the Marciniak–Kuczynski (M–K) analysis for anisotropic materials. It is found that strong cube texture leads to superior formability properties for biaxial stretching while random texture slightly lowers the formability. The strong β-fibre texture of AA6082 in the as-extruded condition leads to reduced formability. The results of the M–K analysis are very conservative compared with the experimental results, and a parametric study is undertaken to investigate the sensitivity of the predicted forming limit curves to some parameters not well defined by the experiments.