Pre-deformation effect on the hot deformation behavior and microstructure of AA6011 tube: experimentation and modelling

Abstract

Hot gas forming (HGF) is an advanced technique for fabricating complex-shaped hollow tubular parts.Practically, multi-step pre-forming involving pre-deformation is often necessary prior to HGF. This paper performs an experimental investigation to simulate the pre-forming operation evaluating the effect of prestrain on the subsequent HGF. Firstly, the dislocation density was accumulated with uniaxial prestretching with different strains (5%, 10% and 15%) at room temperature, simulating the pre-forming operations. Secondly, the sub-sized specimen from the pre-stretched sample was characterized at different temperatures (350, 400 and 450 ℃) to evaluate the effect of pre-strain on successive hot deformation for simulating practical HGF. The experimental results proves the coupled in uence of prestrain and temperature on the ow stress and stress-strain variations. To thoroughly understand the micro-mechanisms, EBSD analysis of grains and grain boundary angles was carried out under different pre-deformation levels and temperatures, which shows the recrystallization phenomenon at 15% prestrain and 450 ℃ temperature. Finally, a physical-mechanism constitutive model is established based on the determined macro and micro results where the pre-strain effect shows the accurate modeling of stress ow behavior of the material.