Selective Laser Melting of Multi-Material Ti15Ta/Ti6Al4V Structures for Biomedical Applications: From Process Parameters to Mechanical Properties and Biological Response

Multi-material structures based on titanium alloys represent a promising approach for the fabrication of functionally graded orthopedic implants capable of combining high mechanical strength with reduced stiffness to minimize the stress-shielding effect. In the present work, multi-material Ti15Ta/Ti6Al4V specimens were fabricated by laser powder bed fusion (L-PBF) for the first time, and the processing parameters of the transition zone were systematically optimized. Three regimes were investigated: baseline (93 J/mm3), double scanning (186 J/mm3), and reduced speed (116 J/mm3). The microstructure and elemental distribution were examined by SEM and EDS; mechanical properties were evaluated through tensile testing and microhardness measurements; biocompatibility was assessed using osteoblasts and gingival fibroblasts. The double scanning regime provided the highest density of the transition zone (99.49%). Tensile failure of the specimens occurred in the Ti15Ta region, confirming the quality of the metallurgical bond. The ultimate tensile strength ranged from 534 to 543 MPa with an elongation at break of 15.7–16.4%. Heat treatment at 875 °C led to the formation of an equilibrium lamellar microstructure and smoothing of the interface. Cell viability on both alloys exceeded 88% as confirmed by flow cytometry and remained above the 70% non-cytotoxicity threshold defined by ISO 10993-5. The obtained results demonstrate the technological feasibility of fabricating multi-material Ti15Ta/Ti6Al4V structures and achieving high-quality metallurgical bonding, which constitutes a necessary first step toward the development of functionally graded orthopedic implants.