Evolution of microstructure and texture during severe plastic deformation of the aluminium alloy AA2099

Abstract

In this work, the effect of high-pressure torsion (HPT) deformation has been investigated for solution-treated (ST) AA2099 aluminium alloy. The strength of the alloy has been found to increase with deformation to an equivalent strain (epsilon(eq)) similar to 27, beyond which it saturates. X-ray line profile analysis and transmission electron microscopy (TEM) revealed an increase in dislocation density and a decrease in grain size till this strain level, beyond which saturation in hardness and grain size occurs. Homogeneous microstructural and mechanical properties are obtained in the steady state regime. A grain refinement down to similar to 80 nm of the HPT-processed specimen in the steady state regime takes place from an initially coarse-grained specimen. The mechanism of grain refinement could be identified primarily as continuous dynamic recrystallization (CRDX). Texture of the HPT material at lower strain levels (similar to 1.8 and similar to 3.5) consists of strong A(1)* and A(2)* simple shear components with very weak B-fibre. Along with ideal components of shear texture, non-ideal components are also observed. Further, increase in strain results in randomization of texture. The weakening of texture at higher strain and the formation of non-ideal texture components is facilitated by grain refinement along with the dynamic precipitation in this alloy.