3D ink-extrusion of elemental powders for high-compliance β-Ti microlattices

Two high-compliance β-Ti alloys – Ti–12Nb–12Zr–12Sn and Ti–6Nb–6Mo–12Zr–12Sn (wt.%) – are manufactured into microlattices via 3D ink-extrusion printing of elemental and hydride powders, followed by sintering and solutionizing at 1400 °C. This study reveals that the formation of “oxygen-rich walls” plays a critical role in triggering embrittlement with intragranular cracking. In compression tests, the Ti–12Nb–12Zr–12Sn microlattices exhibit high compliance (2–6 GPa) but low collapse strength (25–115 MPa) along with semi-brittle behavior, even though stress-induced α” martensite is triggered: stress-strain serrations are explained by the oxygen-rich walls decorated with α plates and athermal ω nanostructures. Nanostructures along these walls are caused by the formation of oxygen-enriched prior particle surfaces during sintering and solutionizing. In contrast, uniform plastic deformation and steady strain-hardening are observed in the Ti–6Nb–6Mo–12Zr–12Sn microlattices whose ductile behavior is consistent with observation of dislocation glide without phase transformation. Its microlattices exhibit very high compliance (6–15 GPa), high yield strength (98–365 MPa) and excellent compressive ductility (>40 %), which are desirable properties for orthopedic implants.