Combined effects of porosity and stress state on the failure behavior of laser powder bed fusion stainless steel 316L

Two primary variables that impact failure behavior of ductile metals are defects and stress state. These factors are especially critical in additively manufactured materials, as components made by additive manufacturing (AM) can have complex shapes that result in the material being subjected to multiaxial stresses under load, and these materials may also contain internal porosity due to AM processing. This study experimentally investigates the effects of both internal pores and stress state on the ductile failure behavior of laser powder bed fusion additively manufactured 316L stainless steel through the introduction of intentional penny-shaped pores of varying size at the center of samples whose geometries result in different stress states. It was found that strain to failure depended strongly on stress triaxiality until a large pore size with a diameter of 1200 um (4% cross-sectional area of the sample gauge sections), while strain to failure was independent of stress triaxiality, and only a function of pore diameter, with larger pores (9% cross-sectional area or larger).