Grain size evolution simulation in aluminium alloys AA 6082 and AA 7020 during hot forward extrusion process

Abstract

The present paper investigates the grain size evolution in aluminium alloys AA 6082 and AA 7020 during hot forward extrusion process. The aim of the present work is the definition and implementation of a predictive algorithm that is able to compute the evolution of the grain shape during the process within the finite element method code Deform. Extrusion experiments were performed at two levels: at reduced scale for investigating and identifying the predictive equations and at industrial scale for validating the developed algorithm. At small scale extrusion, a complete factorial plan was performed for two alloys at three different temperatures, three extrusion ratios and two ram speeds: the discards and extrudates from the experiments were quenched immediately in order to avoid any potential recrystallisation, hence allowing measurements of transitional processing steps. At the industrial scale, instead, the 7020 alloy was extruded with two different die designs, thus producing a 20 mm diameter round bar under different extrusion ratios and strain paths. Finite element simulations were initially validated over visioplastic investigations in order to establish an accurate computation of the material flow, then experimental and numerical results were coupled, thus allowing the definition of the grain evolution model that was successfully integrated and validated on industrial scale trials.

Microstructural and X-ray tomographic analysis of damage in extruded aluminium weld seams

“…Instead, deformation during hot extrusion of the original DC cast grain structure in the dispersoid rich (620) alloy leads to a refined structure of elongated clusters of small grains separated by both low and high angle grain boundaries, partially within the confines of the original, deformed grains through a combination of continuous dynamic recrystallisation and geometric dynamic recrystallisation, as documented by De Pari and Misiolek 48 and further consistent with structures described Güzel et al 49 and Foydl et al . 50 In UA condition, the strength properties are slightly higher than the dispersoid free 621 alloy due to the added effects of the manganese and chromium dispersoids. In comparison with the dispersoid free alloy (621) in UA condition, slightly reduced tensile elongation values are obtained for the T samples.…”

Prediction of Fibrous and Recrystallized Structures in 6xxx Alloy Extruded Profiles

“…with C d is calibration constant equal to 1.48x10 -4 (when grain size and subgrain size are expressed in meters), δ the subgrain size, d 0 the undeformed grain size and ε the effective strain. If the classical assumption for recrystallization kinetics of site saturation and a random distribution of nucleation sites is used, the grain size (at 100% of recrystallized material) can be expressed by: (6) with D a further calibration constant and N the density of recrystallization presented in equation (1).…”

Microstructure Evolution in a 6082 Alloy under Pulsed Magnetic Field Melt Treatment

“…The 6xxx series aluminium alloys contain magnesium and silicon as the main additional elements. They are widely used in the manufacturing of trusses, bridges, automotive components and structural profiles of aircraft structures, which are produced by forging or rolling [1][2][3]. The most commonly used raw material for the forging or rolling process is the direct-chilling (DC)-casting billet.…”