3D ink-extrusion printing and sintering of Ti, Ti-TiB and Ti-TiC microlattices
Titanium metal matrix composite microlattices are fabricated using 3D ink extrusion printing and sintering. The inks consist of TiH2+TiB2 or TiH2+TiC powder blends to form (i) Ti-TiB composites by dehydrogenation and in situ reaction of Ti + TiB2 to form Ti + TiB and (ii) Ti-TiC composites, where TiC remains stable during the sintering process. Rapid densification of the printed powder blend is achieved during pressureless sintering in vacuum at 1200 °C between 1 and 4 h, due to the small Ti particle size available from dehydrogenation of micron-sized TiH2. Near-full density Ti-TiB and Ti-TiC is achieved within individual lattice struts, despite high TiB and TiC volume fractions up to 25 vol.%. The added TiB2 particles are fully dissolved and re-precipitated to TiB whiskers and whisker clusters in <0.5 h. The compressive properties of sintered cross-ply microlattices are measured for the three types of composites (Ti-TiB, Ti-TiC and Ti-TiC(W), with W originating from powder contamination) and pure Ti controls as a function of lattice orientation with respect to load. The compressive strength of the Ti-TiB/TiC composites increases from 55 to 1019 MPa as the designed lattice macroporosity is reduced from 71 to 24 %, and scales with the third power of relative density, indicating a high sensitivity of strength with relative density.