DEFECT STATISTICS AND FRACTURE INITIATION MECHANISMS IN AS-BUILT AND HEAT-TREATED ADDITIVE MANUFACTURED 17-4 STEEL

Defects in additively manufactured metals are detrimental to the manufactured components. Due to the rapid melting and solidification during printing, a non-homogeneous microstructure is typical in the metal specimens additively manufactured using laser powder bed fusion. The present study aims to understand the fracture initiation mechanism in as-built and heat-treated additively manufactured 17-4 stainless steel. To this end, 17-4 stainless steel unnotched and notched specimens additively manufactured using direct metal laser sintering were used. Solution annealing and subsequent aging were performed as the post-heat treatment of the stainless steel test specimens. Postmortem fractography using scanning electron microscopy (SEM) of the fracture surface and micro-computed tomography (micro-CT) of the test specimens before and after fracture revealed that the large coalesced microvoids with sizes greater than 120 ┬Ám significantly influence the ductile fracture initiation in the additively manufactured steel specimens.
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