Microstructure and mechanical properties of 3D ink-extruded CoCrCuFeNi microlattices

Microlattices with orthogonal 0-90 degrees architecture are 3D-extrusion printed from inks containing a blend of oxide powders (Co3O4, CuO, Fe2O3, and NiO) and metal powder (Cr). Equiatomic CoCrCuFeNi microlattices with-170 mu m diameter struts are then synthesized by H 2-reduction of the oxides followed by sintering and interdiffusion of the resulting metals. These process steps are studied by in-situ synchrotron X-ray diffraction on single extruded microfilaments (lattice struts) with-250 mu m diameter. After reduction and partial interdiffusion at 600 degrees C for 1 h under H 2 , filaments consist of lightly-sintered metallic particles with some unreduced Cr2O3. A reduced, nearly fully densified (porosity: 1.6 +/- 0.7%) alloy is obtained after solid-state homogenization at 1050 degrees C for 4 h under H 2 , with a microstructure consisting of two face-centered-cubic phases, one Cu-poor and the other Cu-rich. When a 10 min excursion to 1150 degrees C is added to the 1050 degrees C homogenization, a Cu-rich melt forms which enhances densification (porosity: 0.3 +/- 0.2%) and smooths both strut surfaces and sharp cusps at nodes in the microlattices. The liquid-sintered microlattices show higher compressive strength and ductility than the solid-sintered microlattices. These improvements are consistent with finite-element modeling results which show that smoothening of the sharp cusps at nodes by the solidified melt reduces stress concentrations. These CoCrCuFeNi microlattices can be integrated in more complex load-bearing applications, e.g., as cores of sandwich structures with an unusual combination of high specific stiffness, strength, and toughness.(c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

Microlattices with orthogonal 0-90 degrees architecture are 3D-extrusion printed and synthesized into equiatomic CoCrCuFeNi microlattices through H 2 -reduction and interdiffusion processes. Liquid-sintered microlattices show higher compressive strength and ductility, suitable for complex load-bearing applications.