Shock Mitigation in Additively Manufactured 316L Stainless Steel with Controlled Porosity*

Additive manufacturing (AM) of stainless steels facilitates tuning mechanical properties for unique functionalities, and stainless steel is a prime candidate for use in many applications due to its existing high strength, ductility, and corrosion resistance. AM fabricated stainless steel samples with randomly-placed pores are compared to those fabricated samples with no porosity at a variety of impact speeds to determine the effects of porosity on shock wave propagation and spall failure. Velocity profiles were obtained using photon doppler velocimetry (PDV), and samples were soft-recovered and analyzed post-shock using computerized tomography (CT) and electron backscatter diffraction to investigate void nucleation and coalescence in relation to pore locations. It is observed that the location of the pores in the spall plane affects shock wave propagation, up to and including spall mitigation. Spall failure is observed at a distance away from pores and in front of pores located further from the impact face. However, spall is not present behind pores placed towards the impact face, suggesting that the slowing of the shock waves through strain accommodation around the pores and pore collapse leads to spall mitigation. Further investigation of pores placed in known locations demonstrates shock wave mitigation near the pore even with the presence of a single pore.