Ductile failure in upsetting of a rapid-solidification-processed aluminium alloy

Cold upset-tests have been performed on a Rapid Solidification Processed (RSP) aluminium-alloy, produced by the ‘melt-spun ribbons’-process out of 70% car-scrap and 30% primary scrap. The ribbons are hot extruded, resulting in 29 mm diameter bar. Its properties regarding plastic flow and fracture are strongly anisotropic. Upset-tests are performed on this alloy to verify a concept for the prediction of ductile failure. The experimental results also demonstrate the mechanical integrity of this material. Hill's flow-criterion for anisotropic materials is used in FEM-models of the experiments. Results of various experiments concerning failure at the equatorial free surface are compared with fracture strains in torsion and tension tests in circumferential direction. Furthermore a surface-instability analysis based on an energy principle is applied. It is shown that a graph of effective strain versus triaxiality ( sm/–s ), in addition to an instability-criterion, is a useful tool for the prediction of ductile failure in forming processes.