Prediction of ductile fracture initiation for powder metallurgical aluminum-copper preforms using FEM

Abstract

Background: The deformation of Al-Cu alloys is limited to an intermediate stage due to formation of ductile fracture. The present paper deals with the investigation of the effect of process parameters on the strain paths and ductile fracture initiation of powder metallurgical (P/M) aluminum-copper preforms using FEM during metal forming. Methods: The various Al-Cu preforms were prepared using P/M route. Ductile fracture criterion based on local compressive and tensile strains in combination with FEM was employed to determine the fracture limit. Results: The fracture loci were determined by using experimental method for P/M Al, Al-2wt%Cu, Al-4wt%Cu and Al-6wt%Cu preforms. The results were analyzed for the influence of material composition, initial relative density, aspect ratio and friction on the ductile fracture initiation. The FEM simulations provided detail information on the local compressive and tensile strain paths. Conclusions: The results demonstrate that increase of copper content has decreased the plain ductility limit of the material and, hence the fracture limit decreases. In addition, the fracture limit increases with increase in the initial relative density and aspect ratio or decrease in the tool-work piece interface friction irrespective of the material composition.