Stabilizing post-yielding behavior of a stretching dominated lattice structure through microstructural optimization

Abstract

We investigate the effect of the microstructure on the mechanical response of lattice structures made of a defect tolerant Ti-14 Mo binary alloy fabricated by Electron Powder Bed Fusion. Some of the lattice structures were subjected to different heat treatments to compare different microstructures: a two-phase $\hat{I}\pm$+${\hat{I}}^2$ microstructure inherited from the fabrication (as-built), a full ${\hat{I}}^2$-metastable microstructure, and a ${\hat{I}}^2$-metastable microstructure strengthened via nanoprecipitation of the $\ddot{I}‰$iso phase. We demonstrate that the macroscopic mechanical behavior of one of the most popular stretching-dominated lattice structure, namely the octet-truss, can be tailored through microstructural optimization by increasing the tolerance to plastic buckling of the constitutive struts. Defect-tolerant materials pave the way towards lattice structures fabricated by additive manufacturing with optimized energy absorption performances.