Dynamic compression properties and microstructural evolution of stainless steel 316L fabricated by laser directed energy deposition

Additive manufacturing (AM) has been extensively studied in fabricating metallic components across various industrial sectors, including the automobile and aerospace industries, where the components are usually subjected to dynamic loadings. However, the reported mechanical properties of AM fabricated materials are typically evaluated under quasi-static loading conditions, which cannot satisfy their needs for dynamic applications. In this paper, the dynamic compression properties of stainless steel 316L (SS 316L) manufactured with laser directed energy deposition (L-DED) were studied and their microstructural evolution were revealed. Spilt Hopkinson Pressure Bar (SHPB) technique was utilized in the experiments to achieve various strain rates at 2200, 3300 and 4700 s_1.It was found that the strain rate significantly influences the mechanical properties and microstructural evolution of L-DEDed SS 316L. Under high strain rate loading, twining became the fundamental deformation form, resulting in enhanced strength. However, with further increased strain rate, the rise of adiabatic temperature caused increased stacking fault energy, which then inhibited the twinning behavior. The increase of dislocation density and twinning boundaries (TBs) caused high flow stress through dislocation pileups against the TBs. Adiabatic shear bands (ASBs) appeared at all three strain rates. Subsequently, samples fractured to pieces at 4751 s_ 1 in the ASB areas.