Lithography-based additive manufacturing of steel metamaterials: effect of sintering temperature on shape distortion, microstructure and mechanical properties

Abstract

Lithography metal manufacturing (LMM) is an emerging sinter-based additive manufacturing (AM) technology for support-free 3D printing of extremely complex parts with micrometric resolution on a decimeter scale. Although the printing phase of LMM is well-established, the sintering stage is challenging due to either high porosity or melting-induced deformation, particularly in thin-walled lattices and metamaterials. This study investigates the effects of sintering temperature on shape distortion, surface morphology, chemistry, porosity, microstructure, and mechanical properties of 316L stainless steel auxetic metamaterials 3D printed using LMM and sintered in a furnace customized for precise temperature control. Our results show that the fully dense grain microstructure with high plasticity can be sintering within 1300 – 1325 °C range. Going beyond this temperature results in shape distortion and embrittlement of the steel metamaterials. The previously recommended range of sintering temperatures for 316L steel, 1360 - 1380 °C need revision.