In-Situ Visualization of Tensile Failure in Additively Manufactured 316 L Stainless Steel

Additive manufacturing has become an enabling technology for the production of complicated engineered structures once thought impossible to produce. As these technologies develop, the mechanical behavior of these materials/structures must be characterized in a variety of harsh environments. To assess the loading-rate sensitivity of additively manufactured 316 L stainless steel, dynamic and quasi-static tension experiments were performed. High-speed X-ray phase contrast imaging was performed during dynamic experiments at Argonne National Laboratory's Advanced Photon Source. These images reveal the evolution of porosity and intrinsic defects within the material, and their influence on the mechanisms of dynamic failure in real time. Stress-strain histories were recorded for experiments, on which the performance of the material is addressed. High degrees of localized yielding were observed as a precursor to ductile crack growth and propagation. No transition in the mechanism of fracture was observed. However, from the stress strain-histories the influence of defects was shown to decrease with increasing strain-rates. Comparisons between failure mechanisms of the additively manufactured specimens were made to those of wrought material subjected to identical loading.