Effect of α-phase on the Corrosion Behavior of Ti-3Al-5Mo-4Cr-2Zr-1Fe Alloy

摘要

Ti-3Al-5Mo-4Cr-2Zr-1Fe (Ti-35421) alloy is a newly developed titanium alloy with ideal mechanical properties and lower manufacturing expense. It is well -known that passive film is a main contributing factor to the corrosion resistance of titanium alloys. As the property of passive film is related to the microstructure of alloys, this study aims to investigate the effect of α -phase on the passive film formation and corrosion behavior of Ti-35421 alloy, exploring a method for the fabrication of low-cost and highly corrosion-resistant titanium alloys. The as-received material was ingot forged and rolled Ti-35421 alloy. Metalworking and heat treatments were processed to obtain three groups of samples with different α-phase morphology. T he topography and microstructure of samples w ere characterized using SEM and TEM. The chemical compos itions of passive films and corrosion products were analyzed by EDS and XPS. EIS, potentiodynamic polarization, passivation, and transpassivation tests were conducted to investigate the corrosion behavior of samples. The results show tha t the corrosion beh avior of the Ti-35421 alloy was mainly related to the different morphologies of α-phase, including α lamellar, α lath+equiaxial and αlath+secondary. The dimension and appearance of the α-phase significantly affect the content of TiO2 and the segregation of Ti and Al in the passive films. When the α-phase presented an αlath+equiaxial morphology, the highest TiO 2 content with the lowest Al segregation contributed to the greatest density of passive films and improved corrosion resistance. When the α-phase presented an αlamellar morphology, the lowest content of TiO2 and the highest Al segregation made the passive film the least dense and worst corrosion resistance. When the α phase present ed an αlath+secondary morphology, the increase of the Fe segregation led to moderate corrosion resistance.