Precipitation-induced transition in the mechanical behavior of 3D printed Inconel 718 bcc lattices

This work aims to investigate the effect of microstructure on the mechanical behavior of metallic lattice structures. With that purpose, Inconel 718 bcc lattices were manufactured by selective laser melting and their room temperature compressive behavior was compared in the as-built and aged conditions. A distinct transition from bending-dominated to stretch-dominated behavior takes place following the aging treatment as the as-built supersaturated solid solution (containing a minor fraction of nanoparticles) transforms into a microstructure with a comparatively large fraction of precipitates with dimensions spanning several hundred nanometers. Precipitation leads to a stiffer and stronger structure, with a higher capacity to absorb energy. The obtained mechanical property results are compared to the predictions of the Maxwell criterion and the Gibson-Ashby model for bcc lattices. It is shown that microstructure variations explain, at least partially, the low correlation between the bcc experimental data in the literature with the model predictions.