Anisotropic dynamic compression response of an ultra-high strength steel fabricated by laser hybrid additive manufacturing

Directed energy deposition (DED) is a technological innovation revolutionizing in-situ repair, hybrid manufacturing, and multi-material integration manufacturing, characterized by microstructural heterogeneity on a macro-scale. However, the overall performance of these DED-fabricated components under dynamic loading, particularly along different directions, remains uncharted. This work explores the anisotropic dynamic compression response of an ultra-high strength steel, namely 35CrMnSiA steel, fabricated using DED on a wrought substrate. The laser hybrid additive manufactured samples were subjected to split Hopkinson pressure bar testing along different directions. The results show the following: 1) hybrid manufactured 35CrMnSiA steel has an anisotropic dynamic compression response due to the mismatched properties of each subzone induced by microstructural heterogeneity, 2) low-strength DED part shows higher strain under compression along the build direction but behaves similarly to the wrought material when compressed along the transverse direction, 3) intergranular void/crack is the primary damage mechanism, cracks preferred formed in wrought substrate due to the martensite with poor plastic dissipation ability, 4) when the interface is subjected to parallel directional impact loads, the strain mismatch between the two side subzones leads to interface separation. This study provides comprehensive understanding of the dynamic behavior of DED-fabricated components with heterogenous microstructure, and new insight into demanding tailored strategies to ensure consistent and predictable behavior under various loading conditions.