Engineering strength-ductility balance in Ti-15Zr alloy with corrosion resistance

Titanium alloys are attractive materials, but achieving a balance between high strength and adequate ductility remains challenging. In this study, a two-pass cold drawing process with intermediate annealing was applied to a Ti-15Zr alloy. The microstructural evolution, characterized by EBSD and TEM, reveals a transition from a high-density dislocation substructure to a recrystallized coarse-grained state. As the annealing temperature increased from 350 to 450 °C, the tensile strength decreased from 1129 to 1049 MPa, while the elongation substantially increased from 7.7 % to 15.1 %. Notably, the 450 °C treatment provided an optimal recovery substructure, facilitating the formation of nanotwins during the subsequent cold drawing, which effectively impeded dislocation motion and preserved high strength while enhancing plasticity. When the annealing temperature reached 550 °C, significant grain growth occurred, leading to a sharp decrease in tensile strength. Electrochemical tests showed that fine grains enabled a denser passive film, CD-350 exhibited the highest corrosion resistance, followed by CD-450. All samples confirmed excellent cytocompatibility in vitro. Therefore, intermediate annealing at 450 °C enables the production of Ti-15Zr alloy with a superior strength-ductility balance, acceptable corrosion resistance, and satisfactory biocompatibility, making it a preferred material for dental implant applications.