Phase-Tunable Fabrication of Consolidated (α+β)-TiZr Alloys for Biomedical Applications through Molten Salt Electrolysis of Solid Oxides

Electrochemical reduction of a solid TiO 2 -ZrO 2 mixture (molar ratio = 1:1 to the TiZr alloys in a consolidated porous structure was studied by constant cell voltage electrolysis in molten CaCl 2 at 900 °C. For the first time, and surprisingly, it was found that tuning the α- and β-phases in the TiZr alloys could be easily realized by controlling the electrolysis time or, specifically, the oxygen content in the alloys. Oxygen acted as a phase-transition inhibitor from the high-temperature β-TiZr to the low-temperature α-TiZr, leading to metastable β-TiZr or (α+β)-TiZr as the product at room temperature. However, if the oxygen content decreased to < 1100 ppm, only α-TiZr was collected, even when the electrolytic alloy was directly quenched in water. The consolidated porous (α+β)-TiZr alloys possessed elastic moduli in the range of 20-40 GPa, matching closely to that of natural bone (10-30 GPa). They also exhibited excellent corrosion resistance in the Ringer solution. These novel findings promise a simple, one-step, low-energy, and environmentally friendly electrochemical process for the production of β-phase containing TiZr alloys as medical implant materials without any added expensive and/or bio-incompatible elements.