Non-equilibrium microstructure, crystallographic texture and morphological texture synergistically result in unusual mechanical properties of 3D printed 316L stainless steel

Mechanisms underlying the evolution of texture and microstructure during selective laser melting (SLM)and their combined effects on the mechanical response of 316L stainless steel are presented. Long columnar grains with a fiber texture <110> || build direction (BD)evolved in the SLM printed material. Fiber texture was stronger in the horizontal build compared to the vertical build. Use of bidirectional scanning strategy enforced epitaxial growth of grains across melt pools present within a single printed layer. <110> || BD texture evolved as a consequence of maintaining the balance between epitaxy and growth of [100]along maximum thermal gradient. High dislocation density and not grain size effect of the ultra-fine cellular structure, imparted high strength to 316L. Lower average Schmid factor and smaller effective grain size in the horizontal build by virtues of crystallographic and morphological textures, respectively, imparted higher yield strength than the vertical build. The horizontal build demonstrated higher strain hardening rate in the early stages of deformation compared to the vertical build due to higher crystallographic texture dependent twinning. However, the higher rate of dislocation annihilation led to a continuous decline in the strain hardening rate of the horizontal build. In contrast, a stable strain hardening rate was maintained in the vertical build, which led to higher ductility than the horizontal build. In summary, the roles of non-equilibrium microstructure and texture (crystallographic and morphological)in regulating mechanical properties elucidated here, can be utilized in designing additively manufactured structural components of 316L stainless steel.