Fracture Initiating Mechanism in Additively Manufactured 17-4 Stainless Steel

Abstract

Additive manufacturing provides exceptional geometrical freedom to the designers and enables the production of parts that cannot be made through subtractive processes. Defects in additively manufactured (AM) metals are detrimental to the manufactured components. This study aims to understand the fracture initiation mechanism in as-built AM 17-4 stainless steel. Micro-computed tomography (micro-CT) analysis was conducted on the undeformed and fractured unnotched and notched specimens to characterize the defects in the as-printed specimens before and after deformation. The micro-CT analysis showed that the initial void count and volume fraction increased after the deformation indicating new void nucleation and dilation of voids. Furthermore, coalesced void colonies were noticed in the fractured specimens in the vicinity of the fracture surface. Evidence for void nucleation, dilation, and coalescence indicates ductile fracture to be the fracture initiation mechanism in AM 17-4 steel.