Assessment of β stabilizers additions on microstructure and properties of as-cast β Ti–Nb based alloys

The novelty of the present work lies in elucidating the correlation of Moeq with mechanical and surface parameters. The Ti–15Nb (TN-15), Ti–40Nb (TN-40), Ti–33Nb–33Zr (TNZ-33), Ti–40Nb–40Zr (TNZ40) and Ti–35Nb–7Zr–5Ta (TNZT) alloys were obtained by casting. The alloys were formed by β-Ti grains with a micrometric morphology, except the as-cast TN-15 alloy formed by α + β. Adding Nb and Zr influenced the lattice parameters of phase β, as well as the crystal structure. Grain size (GS) decreased adding Nb and Zr following this relation: TN-40 > TNZ-33>TNZT > TNZ40. The roughness decreased with rising Nb and Zr contents being in the range of 1.3–3 μm, and it was possible to correlate it with the Moeq. The contact angle and free energy surface values were inversely proportional, and the as-cast TNZ40 alloy with smaller GS was less wettable (60) than TN40 (GS: 1423 μm). The mechanical properties decreased to Moeq of 14.9 wt% then their significantly went above this value, except for the as-cast TN-15 alloy (E: 65 GPa, microhardness: 264 HV) formed mainly by a hardener phase α. Both elastic modulus and microhardness showed the same tendency as the Moeq values and the cell parameter of phase β (aβ). The oxygen content was all in accordance with ASTM E1409-13 for applications as metallic biomaterials being in the range of 0.044–0.195 wt%.