Extrusion of different aluminium alloys ; experimental work and modelling treatments

Abstract
The present work reports on modelling of extrusion of both generic and commercial alloys. The uniqueness of the work is the coupling of microstructural based models and FEM-models applied and validated both on laboratory and industrial scales. The extrusion trials were carried out at the laboratory press at SINTEF and at an industrial press at SAPA. Focus in that respect was on the extrusion productivity in terms of ram loads (deformation resistance). Correlations between flow stresses obtained in torsion tests and uniaxial compression tests and the extrudability parameters (breakthrough force and die force) for the same materials and same preheating and processing conditions have been studied. The finite element codes ALMA and FIDAP have been coupled with a microstructural based flow stress model (ALFLOW) and tested on the experimental observations. The constitutive parameters for the different alloys, which is an important input in the ALMA model has been obtained by the ALFLOW model (which has been verified by experimental results in torsion and uniaxial compression). In the case of the ALMA model the predictability of extrusion forces of the investigated alloys are very good. The FIDAP predictions of the industrial extrusion trial are also in reasonable agreement with the experiments. In general, it has been shown that the FEM simulations are very sensitive to the applied constitutive equation and the material constants in this equation.