Effect of Contours on the Mechanical Behavior of Metal Extrusion Additive Manufacturing Parts: A Study on Notched 17-4PH Stainless Steel

Abstract

Material extrusion allows for the fabrication of metallic parts with competitive cost and flexibility in setting fabrication parameters. However, the parts contain defects that are due to the deposition route itself and to the removal of polymers during debinding and sintering. These defects affect the mechanical properties. It is therefore necessary to assess the mechanical properties of the parts with respect to such processing parameters. In this paper, the relationship between two configurations of notch, deposited layer thickness, and the mechanical response of additively manufactured metallic samples is analyzed. The presence of contours in the notch significantly affects the mechanical response. Samples with a machined notch and a 50-μm deposited layer thickness led to brittle fracture, while those with a 125-μm layer thickness experienced stable crack propagation before failure. The deformation mechanisms varied depending on the notch configuration, with strain concentrations at contour boundaries for samples with additively manufactured notches. The crack propagation strongly correlated with the sample mesostructure, often following the ±45° orientation of deposited layers. Debonding at the boundary between the last contour and the infill zone was a common failure mode for the studied samples.