Electrochemical Activity and Corrosion Behavior of Ultrafine-Grained Ti-xMo Alloys Processed via Powder Metallurgy

Titanium alloys are widely used for biomedical implants due to their favorable mechanical properties, corrosion resistance, and biocompatibility. However, the development of multifunctional implant materials requires not only structural stability but also controlled electrochemical responsiveness, an important property for electrochemical sensing. This study developed ultrafine-grained Ti-xMo alloys (x = 28 and 31 wt.%) via mechanical alloying followed by powder metallurgy to investigate the effect of high Mo content on phase stability, corrosion behavior, and electrochemical sensing response. Both alloys exhibited predominantly β-phase microstructures, with β-phase fractions exceeding 93%, confirming effective stabilization at elevated Mo concentrations. Electrochemical tests conducted in 0.01 M PBS and Ringer's solution revealed that pure Ti exhibited the highest impedance modulus and lowest corrosion current density, indicating superior passive film barrier properties. In contrast, high-Mo alloys showed reduced polarization resistance and increased charge-transfer contribution, associated with modifications in passive film defect chemistry and electronic properties induced by Mo enrichment. Among the investigated compositions, Ti-31 wt.% Mo demonstrated improved electrochemical stability compared to Ti-28 wt.% Mo, exhibiting lower corrosion current density and higher impedance values within the high-Mo regime. Cyclic voltammetry performed in 0.01 M PBS containing 1 mM K₃[Fe(CN)₆] confirmed enhanced heterogeneous electron-transfer capability for Mo-rich alloys relative to pure Ti. Overall, Ti-31 wt.% Mo provides a balanced combination of β-phase stabilization, moderate corrosion resistance, and improved electrochemical responsiveness potentially suitable for sensing interfaces.