Effect of Yttrium on corrosion resistance of Zr-based alloys in Ringer's lactate solution for biomaterial applications.

In this study, several types of zirconium-based alloys supplemented with 2, 3, and 4, in wt.% of yttrium for corrosion resistance enhancement were investigated. The specimens were prepared by a single arc welding furnace in an argon-controlled atmosphere. By optical and scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and electrochemical tests, the effect of different portions of yttrium on the surface morphology, phase structure, and corrosion resistance in the Zr alloys were analyzed. As of result of arc welding, the specimens were obtained and examined by optical microscope and then homogenous structures were observed. These structures are matrix (Zr-rich) and oxides. Furthermore, as of the characterization results by X-ray diffraction, the main compound of the alloys was Zr6Mo6AlTi, while others were AlZr3, MoO2, ZrO2, and Y2O3 oxides. Yttrium addition in the alloys prior to the corrosion test led to thickened grain boundaries but reduced grain size. The Y2O3 itself remained at the grain boundaries as clusters. The corrosion test was performed in Ringer's lactate solution by using anodic polarization. The effect of yttrium addition into Zr-based alloys was found to be beneficial by shifting the corrosion potential toward a positive value. Zr-6Mo-6Al-Ti-4Y had a higher open corrosion potential value than the other two alloys. The difference was approximately 200 mV. However, the passive region of Zr-6Mo-6Al-Ti-4Y was the shortest and broke down at an earlier stage. The formation of these kinds of oxides was the reason for the increase in corrosion potential of Zr-based alloys with 4% Y added. [ABSTRACT FROM AUTHOR]