Additive manufacturing of a low modulus biomedical Ti–Nb–Ta–Zr alloy by directed energy deposition

While β titanium alloys have garnered extensive attention as a new generation of biomedical materials designed to mitigate stress shielding due to their low modulus, the realm of additive manufacturing for these alloys is still in its nascent stages. This study focuses on the additive manufacturing of Ti–35Nb–5Ta–7Zr alloy powder via directed energy deposition (DED). The primary objectives were assessing the feasibility of employing DED for this alloy powder and identifying processing parameters to achieve nearly dense components. Systematic exploration of the effect of various processing parameters was performed, and the resultant impact on the densification of the produced specimens was studied. Comprehensive analysis of the microstructure, mechanical properties, electrochemical behavior, and cell studies of fully dense sample coupons were performed. These fully dense samples were found to exclusively comprise the β phase of titanium, resulting in a reduced modulus of elasticity (approximately 44–47 GPa) resulting in high yield strength to elastic modulus ratio. Microstructural examinations revealed the presence of both columnar and equiaxed dendrites, with grains transitioning from columnar to equiaxed (known as CET). Electrochemical testing of the coupons indicated exceptional corrosion resistance in the additively manufactured TNZT alloy. Pre-osteoblasts cultured on the alloys showed good attachment, viability, and growth to confirm cytocompatibility. These findings unveiled the attainment of high strength, favorable ductility, a low elastic modulus, excellent corrosion resistance, and cytocompatibility in dense samples created via DED of Ti–35Nb–5Ta–7Zr. These outcomes hold immense significance for the production of patient-specific medical implants manufactured from β-Ti alloys.