Effect of annealing temperature on the microstructure and corrosion behavior of Ti-6Al-3Nb-2Zr-1Mo alloy in hydrochloric acid solution

The corrosion behavior of Ti-6Al-3Nb-2Zr-1Mo alloy annealed at 800 ?C, 900 ?C, 960 ?C and 1040 ?C was investigated in 5 wt. % hydrochloric acid (HCl) solution using open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. It was found that the Ti-6Al-3Nb2Zr-1Mo alloy annealed at 1040 ?C exhibited the best corrosion resistance. While the Ti-6Al-3Nb-2Zr-1Mo alloy annealed at 960 ?C exhibited the least corrosion resistance. The difference in corrosion rate of Ti-6Al-3Nb-2Zr1Mo alloy annealed at different temperatures was obtained by weight loss experiments in 20 wt. % HCl solution. The results showed that the corrosion rate of the Ti-6Al-3Nb-2Zr-1Mo alloy annealed at 960 ?C was the highest, followed by the alloys annealed at 900 ?C and 800 ?C, while the corrosion rate of the Ti-6Al-3Nb-2Zr-1Mo alloy annealed at 1040 ?C was the lowest, which was consistent with the results of the electrochemical experiments. The initial corrosion morphology of the Ti-6Al-3Nb-2Zr-1Mo alloy in 20 wt. % HCl solution was observed by scanning electron microscopy (SEM). The SEM images revealed that ?/? phase boundaries were preferential sites for corrosion attack, and the ? phase exhibited preferential dissolution in comparison to the ? phase. First principle calculations proved the existence of microgalvanic cells, which accelerated the corrosion of the ? phase. The results indicate that Ti-6Al-3Nb-2Zr-1Mo alloy corrosion behavior in HCl solution is predominantly affected by the fraction and grain size of ? and ? phase.

Automated summary

The corrosion behavior of Ti-6Al-3Nb-2Zr-1Mo alloy in HCl solution is affected by annealing temperature, with higher temperatures enhancing corrosion resistance. Lower annealing temperatures result in higher corrosion rates.