In-situ observation of asymmetrical deformation around inclusion in a heterogeneous additively manufactured 316L stainless steel

Oxide inclusions widely exist in additively manufactured components due to the native oxide layer on the powder surface, together with gas impurities during the printing process. Using in-situ tensile tests combined with electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) techniques, we propose an asymmetrical cracking mechanism around the oxide inclusions in a selective laser melted 316L stainless steel. The heterogeneous sub-micro cellular structures lead to different twinning tendencies around the inclusions due to the size-related critical twinning stresses, and the deformation-induced nano-twin clusters can resist the cracking propagation, therefore resulting in the asymmetrical cracking behaviors around the inclusions.