Near-full density enabled excellent dynamic mechanical behavior in additively manufactured 316L stainless steels

• SLM-316L exhibit much larger sensitivity to defects on the dynamic mechanical response than the quasi-static case. • Intrinsic pore defects should be responsible for the anisotropic spallation behavior of the SLM-316L. • Dislocation slip dominates the spallation mechanism, accompanying by a small amount of twinning and martensite transition. Mechanical properties of additively manufactured alloys are momentously affected by the fabrication defects, thus limiting their applications in extreme conditions. Here we report on a near fully dense 316L stainless steel via optimized laser processing parameters. The results reveal that the dynamic mechanical response exhibits much greater sensitivity to defects than the quasi-static one. The densest specimen (porosity < 0.01 %, 260W-316L) exhibits superior spall strength of 3.87 GPa and negligible damage fraction of 0.03 % at peak stress of 4.8 GPa, which are 12 % higher and 92 % smaller than those of 0.18 % porosity specimen (300W-316L). For both horizontal and vertical impacts, hardly any anisotropy of spall strength is observed in 260W-316L, demonstrating the crucial role of the pore defects on the dynamical behavior. Moreover, dislocation slip dominated spallation mechanisms have been observed in the additively manufactured 316L specimens, accompanied by a small amount of deformation twinning and martensitic transitions. This comprehensive understanding of the defect-dependent spallation behavior and deformation mechanisms provides valuable insights for optimizing the dynamic mechanical properties of additively manufactured metals and alloys.