Modelling central bursting in the extrusion of particulate reinforced metal matrix composite materials

Abstract

Elastic-viscoplastic damage constitutive equations for particulate reinforced metal matrix composite (MMC) materials have been used to investigate central burst formation in extrusion. The equations have been implemented into finite-element software with which extrusion processes for a range of area reductions and volume fractions of particulate reinforcement have been simulated. The analyses carried out have enabled an extrusion limit diagram to be established for a particle reinforced aluminium matrix composite. The results show that for volume fraction of reinforcement up to approximately 20%, the influence of the volume fraction of particle on central bursting is small compared with the process parameters area reduction and semi-cone die angle. Hence, the method of selection of process parameters to avoid central bursting in MMC materials is likely to be the same as that for monolithic materials. The results show that with increasing volume fraction of reinforcement, significant changes in the patterns of damage evolution occur, with increasing volume fraction leading to the development of damage in the central region of the extrudate that does not exist for lower volume fractions. However, increasing the volume fraction of reinforcement tends to decrease the level of surface damage developing within the extrudate.