Enhancing the bond strength in meta-crystal lattice of architected materials

TL;DR

This paper investigates how the build angle and inherent defects in 3D-printed meta-crystal lattice structures influence their mechanical strength, revealing defect-driven strengthening mechanisms that can be exploited to enhance bond strength.

Contribution

It demonstrates that intrinsic defects like dislocation networks can be harnessed to improve the bond strength of meta-crystal structures manufactured via selective laser melting.

Findings

Build angle significantly affects defect formation.

Inherent microstructural defects can enhance strength.

Micro-segregated structures overcome strength-ductility trade-offs.

Abstract

Architected materials produced by powder bed fusion metal additive manufacturing technique offer realization of complex structural hierarchies that mimic the principles of crystal plasticity while still being ultralight-weight, though suffering from deep-rooted multiscale defects including microstructural heterogeneity caused by the complex thermo-mechanical transients in the melt pool. Here we manufacture meta-crystal 316L stainless steel microlattice structures by selective laser melting process for utilizing the strain localization mechanism in bulk structures akin to dislocation slip mediated plasticity. The build angle was observed to be the primary influencer of defects generated and the presence of inherent voids was the major drawback that would undermine their structural performance as mechanical metamaterials. However, other defects in the form of spatially correlated dislocation networks and micro-segregated cellular substructures overcome the strength-ductility trade-off and render the bulk structures comparable to other engineering materials including conventional steels. By exploiting this intrinsic strengthening mechanism, the bond strength of meta-crystals (i.e. strut strength) can be enhanced (or controlled) on top of employing hardening principles of metallurgy to design materials with desired properties.