Individual influence of forming parameters on surface recrystallization during aluminium extrusion

Abstract

It is well-known that during extrusion of aluminium alloys, the operating parameters (extrusion ratio, ram speed, billet temperature and extrusion mode) influence subsequent surface recrystallization. Research has been made on the influence of some parameters but the individual influence of each parameter is not clear. In this study, the respective influence of the major parameters is studied using the Taguchi method combined with finite element method (FEM) simulation. The Taguchi method was adopted to establish the sequence of the simulations and to analyse the influence of each parameter. Modelling of microstructure evolution during the aluminium extrusion process was combined into the FEM code Forge2®. The following simulation results were obtainable using this metallurgical model: subgrain size, volume fraction recrystallization and recrystallized grain size. The other results, the peak load, the temperature and the load in the so-called 'quasi-static' extrusion, were also obtained. The calculated results were in reasonable agreement with the experimental data now available. In this study, to obtain meaningful results, the friction coefficient was first evaluated by the inverse method. Subsequently a group of simulations was performed with different extrusion parameters. The analysis showed the extrusion ratio and the extrusion mode had greater influence than the other parameters on surface recrystallization.