On the Characterization of Fracture Forming Limits for Highly Ductile Metals Through Radial Extrusion

This paper introduces a new test based on the double-action radial extrusion concept to characterize bulk formability of highly ductile metals. The test is carried out in a multidirectional tool system and the methodology involves determination of the strain loading paths up to fracture through combination of digital image correlation and force-time evolutions. Strain loading paths together with finite element modelling and fractography analysis by means of scanning electron microscopy allows characterizing the crack opening modes. Results in as-deposited wire additive manufactured aluminum specimens show that material flow at the radially extruded flanges gives rise to crack opening by out-of-plane shear and tension. The new test is adequate to determine the fracture limits of highly ductile metals, which cannot (or are very difficult to) be obtained by conventional upset bulk formability tests.