In-situ observation of deformation-induced grain reorientation in 718 Ni alloy microlattices

Abstract

Microlattices pose ample opportunity for constructing light weight structures for the automotive and aerospace industries. Laser powder bed fusion is an appealing technique to fabricate these structures because of its capabilities to process high-resolution complex architectured structures. In this work we explore the use of a 718 oxide dispersion strengthened alloy to create three microlattice structures designed in nTop, a straight bar, honeycomb and body-centered cubic (BCC) microlattice and investigate the effects of architectures on tensile behavior of the microlattices in a scanning electron microscope. The straight bar configurations deliver high strength but low ductility. The BCC lattices are highly deformable but soft. The honeycomb has an attractive combination of high strength and pronounced work hardening. Furthermore, electron backscattered diffraction studies revealed substantial crystallographic reorientation and grain refinement in the honeycomb lattice during deformation, in contrast to little crystal orientation change in the straight bar specimens. This study suggests that architectures play a significant role in the tensile behavior and deformation mechanisms in metallic materials.