Metal material extrusion of titanium using a simple partially biobased binder system formulation

This study presents the development and evaluation of a novel titanium feedstock for metal material extrusion additive manufacturing, using a partially bio-based backbone system composed of polylactic acid and polybutylene adipate terephthalate. To improve printability and flexibility, various combinations of polylactic acid/polybutylene adipate terephthalate and thermoplastic elastomers were investigated. Seven distinct binder formulations were prepared using 55 vol% Ti–6Al–4V powder and analyzed through systematic extrusion, printing, solvent, and thermal debinding trials, as well as sintering. Among them, a formulation containing 15 vol% polylactic acid, 25 vol% polybutylene adipate terephthalate, and a medium-hardness thermoplastic elastomer exhibited superior printability, enabling reliable extrusion at speeds up to 20 mm/s. Increasing the powder content to 58 vol% in this optimal formulation yielded dense green parts suitable for thermal debinding and sintering. The sintered samples achieved a high relative density of approximately 97% and expected shrinkage and favorable microstructural characteristics. Scanning electron microscopy revealed a dense microstructure with minor porosity and titanium carbide precipitates predominantly localized in the grain centers, attributed to limited carbon residue from the binder system. These results demonstrate that a polylactic acid/polybutylene adipate terephthalate backbone system is a sustainable and effective option for metal material extrusion of titanium.