On material flow and aspects of structural modification during direct and indirect extrusion of aluminium alloy

Abstract

In this paper, both direct and indirect extrusions are simulated using a viscoplastic constitutive model. The simulated velocity fields for both direct and indirect extrusions are discussed and compared with experimental results. Advanced numerical techniques are used to trace backward and forward discrete particles of the billet. The effect of friction on the material flow is discussed. Back-end defects are simulated and practical methodologies are derived to minimise such defects using finite element modelling (FEM). Peak loads, temperatures and strain rate distribution are also compared between direct and indirect extrusions. Numerical subroutines have been developed and integrated into the FEM software in order to introduce the possibility of prediction of microstructural evolution. The results of such numerical simulations to increase productivity within the extrusion industry are currently limited only by the lack of sufficient physical metallurgical detail and by obstacles preventing the FEM simulation to be directly applied. This aspect is discussed in some detail.

Keywords:

• Aluminium alloys
• Extrusion
• FEM
• Material flow
• Microstructure