Effects of Lattice Architecture, Nominal Feature Size and Heat Treatment on the Tensile Behavior of L-PBF-Fabricated Inconel 718 Lattice Structures

Laser powder bed fusion (L-PBF)-fabricated Inconel 718 lattice structures offer considerable potential for lightweight load-bearing applications, but their mechanical integrity depends on architecture, geometric scale, manufacturing defects, and post-processing condition. This study examined the combined effects of Diamond, Gyroid, and Octet architectures, nominal feature sizes of 1.0, 1.25, and 1.5 mm, and four heat-treatment conditions on tensile behavior and fracture characteristics. The specimens were evaluated using explicit-dynamics finite element analysis, room-temperature quasi-static tensile testing, and SEM fractography. A feature-size-dependent reversal in architecture ranking was observed: Gyroid exhibited the highest mean apparent tensile strength among the 1.0 mm lattices across the investigated heat-treatment conditions, whereas Diamond exhibited the highest mean apparent tensile strength among the 1.5 mm lattices across the same conditions. HT-C shifted the tensile response toward higher apparent strength and lower apparent deformation capacity, whereas selected HT-B-treated specimens exhibited more ductile fracture morphologies. These findings show that architecture, nominal feature size, and post-processing condition must be considered jointly when designing L-PBF Inconel 718 lattice components within the investigated design range.