Microstructure and Processing of 3D Printed Tungsten Microlattices and Infiltrated W–Cu Composites

Tungsten is of industrial relevance due its outstanding intrinsic properties (e.g., highest melting-point of all elements) and therefore difficult to 3D-print by conventional methods. Here, tungsten micro-lattices are produced by room-temperature extrusion-based 3D-printing of an ink comprising WO₃–0.5%NiO submicron powders, followed by H₂-reduction and Ni-activated sintering. The green bodies underwent isotropic linear shrinkage of ≈50% during the thermal treatment resulting in micro-lattices, with overall 35–60% open-porosity, consisting of 95–100% dense W–0.5%Ni struts having ≈80–300 μm diameter. Ball-milling the powders and inks reduced the sintering temperature needed to achieve full densification from 1400 to 1200 °C and enabled the ink to be extruded through finer nozzles (200 μm). Partial sintering of the struts is achieved when NiO is omitted from the ink, with submicron interconnected-porosity of ≈34%. Several tungsten micro-lattices are infiltrated with molten copper at 1300 °C under vacuum, resulting in dense, anisotropic W–Cu composites with 40–65% tungsten volume fraction. Partially sintered struts (containing nickel) with submicron open porosity are also infiltrated with Cu, resulting in co-continuous W–Cu composites with wide W struts/Cu channels at the lattice scale (hundreds of micrometers), and fine W–Cu interpenetrating network at the strut scale (hundreds of nanometers) allowing for the design of anisotropic mechanical and electrical properties.