A preliminary investigation of gyroids made of W-Cu composite materials produced by investment casting into SiO2-based molds 3D-printed by stereolithography

In this work, a new indirect additive manufacturing technique to produce tungsten-copper composites (W-Cu) triply periodic minimal surface (TPMS) geometries by investment casting is proposed. The process consists in the combination of stereolithography (SLA) and molten copper casting to realize complex architectures (i.e., gyroids) and to control the volume fractions of W and Cu, tailoring the composite properties. SiO2-based tubular molds were produced by SLA to reproduce the negative of the object to be casted. The positive shape of the final object was obtained by filling the cavity of the SiO2 mold with a mixture of tungsten and corn starch (CS), which was used as space holder. After a pyrolysis stage at high temperature, the W porous structure was infiltrated by melted copper under vacuum. The leaching of the SiO2 mold using a basic solution allowed obtaining the final geometry. W-based particles of different diameter (i.e., d50 = 10, 22, and 150 µm) were used, and CS content was changed between 5 and 30 %vol. (with respect to W) to adjust the copper content in the composite. In all cases, produced samples retained the geometric properties of the CAD design.