Geometry‐Assisted Phase Selection: Interplay of Phase Heterogeneity and Geometry in Gyroid Shell Metamaterials Printed with 17‐4 PH Stainless Steel

Microstructural control is both a major challenge and an opportunity in additive manufacturing of parts, and plays a particularly dominant role in the performance of components with complex geometries. Much effort has gone into metal additive manufacturing of metamaterials; yet a thorough understanding of microstructural controllability toward optimized part performance is lacking. Of interest is the development of functionally graded metamaterials, which locally optimize part properties to enhance overall part performance. 17‐4 precipitation hardened (PH) stainless steel has previously been shown to exhibit phase control as a function of printing parameters; yet the influence of geometry on phase evolution in printing of complex structures and metamaterials has so far remained unexplored. The present study aimed at elucidating the relationship between phase evolution and geometry in gyroid shell metamaterials printed in 17‐4 PH steel via laser powder bed fusion. Local hardening is demonstrated to occur as a function of geometry, likely prompted by topology‐induced variations in cooling profiles. The associated phase evolution is governed by the gyroid geometry and strongly correlates with geometry‐dependent loading paths therein. This demonstrates the possibility of inducing functional grading through geometric complexity, highlighting the possibility of significant property enhancements through local microstructural control.