Significant anisotropy in mechanical properties was observed in 316L stainless steel (SS) that was subjected to selective laser melting (SLM) to produce a hierarchical structure, composed of molten pool, columnar grains, and a cellular substructure. Such anisotropy was induced by the geometric relationship between the boundary of the molten pool and the tensile force. The in situ tensile test showed initial deformation rapidly occurred at the boundary of the molten pool, followed by strain localization, and a lower ductility was obtained when loaded in the longitudinal direction (perpendicular to the molten pool). By contrast, the deformation was significantly constrained because of the geometry of the boundary of the molten pool, and substantial deformation occurred in the cellular substructure during loading in transverse direction (parallel to the molten pool). Finally, the quantitative analysis revealed that the high-level strength was attributed to the high-density dislocations and the fine cellular substructure.

Mechanical anisotropy behaviors are investigated in slightly rolled Inconel718 alloy with string-like δ phase and carbides produced during various solid-solution and aging treatments. A weak anisotropy in the strengths and rupture properties at 650 °C is visible, whereas ductility, i.e., reduction in area (RA) and impact toughness (CVN), presents a sound anisotropy behavior. MC carbides promote the operation of slip systems and thus are conducive to weakening the strength anisotropy. The RA anisotropy mainly stems from high-density δ phase particles that provide more crack nucleation sites and stimulate rapid propagation because of the shorter bridge distance between micro-cracks at the rolling direction. In contrast, CVN anisotropy arises from both δ phase and carbides at a lower solid-solution temperature of 940 °C but only depends on carbides at 980 °C where the δ phase fully dissolves. Apart from dislocation motions operated at room temperature, the activated grain boundary processes are responsible for the weak anisotropy of rupture properties at the elevated temperature. This work provides a guideline for technological applications in the hot working processes for Inconel718 alloys.