An experimental and numerical study on the formability of textured AlZnMg alloys

The influence of texture and grain structure on strain localisation and formability is investigated experimentally and numerically for two AlZnMg alloys. The considered alloys have recrytallised or non-recrystallised grain structure and strong or nearly random texture. The textured materials have rotated cube texture or beta-fibre texture of high intensity. A comprehensive test programme, including uniaxial tension tests in three directions, through-thickness compression tests, plane-strain tension tests and double-plate formability tests, is completed to determine the work hardening, plastic anisotropy and formability of the materials. Strain localisation and failure are examined by optical microscopy. Using parts of the test data, an anisotropic plasticity model is calibrated and applied in calculation of forming limit curves, using the Marciniak-Kuczynski (M-K) analysis for anisotropic materials. The formability tests show that the materials with nearly random texture exhibit superior formability. This is mainly attributed to enhanced work hardening for these materials. For the material exhibiting strong P-fibre texture significantly lower formability is found in equibiaxial stretching than in plane strain, while this characteristic is not seen for the material with strong cube texture. The M-K analysis is capable of predicting the major trends of the experiments, and captures the low formability of the alloy with strong beta-fibre texture under equibiaxial straining. A numerical study is performed to evaluate the sensitivity of the predicted forming limit curves to parameters not determined experimentally. (C) 2007 Elsevier Masson SAS. All rights reserved.