Comprehensive analysis of corrosion resistance and micro-machinability properties of α + β and β phase novel Ti-30Zr-5Mo biomedical alloys

Abstract

The biocompatibility and corrosion resistance of biomedical alloys are crucial to preventing adverse tissue reactions and maintaining implant integrity. Additionally, machinability is essential for producing implants with complex shapes and high surface quality. This study investigates the biocompatibility and micro-machinability of Ti-30Zr-5Mo alloys with different phase compositions: forged (mostly α), solution-treated at 600 °C (α + β), and 700 °C (only β). Biocompatibility was evaluated through electrochemical corrosion tests under in-vitro conditions, while machinability was assessed via micro-milling tests. The corrosion rate of the β-phase alloy was approximately 3.5 times lower than the forged (9.08 nm/year) and 600 °C-treated alloys (9.85 nm/year), attributed to its stable and uniform structure. The forged sample exhibited the lowest corrosion resistance due to its heterogeneous α + β structure, with microgalvanic corrosion observed. Additionally, the forged alloy, with a high α phase content, showed higher cutting forces (21.5 N) and burr widths (230 μm). As the solution treatment temperature increased, the α phase decreased, leading to lower cutting forces and burr widths. The β-phase alloy (700 °C) showed about a 60 % reduction in cutting forces (8.5 N) and an 8-fold decrease in burr widths (28 μm) in up-milling compared to forged sample, indicating superior machinability under micro conditions.