Microstructure and corrosion behavior in SBF medium of spark plasma sintered Ti-xZr-20Si-10B (x = 5, 7, 10, 15, 20 at.-%) alloys

This work aims to evaluate the microstructure and corrosion behavior in SBF medium of spark plasma sintered Ti-xZr-20Si-10B (x = 5, 7, 10, 15 and 20 at.-%) alloys. Metastable Ti-Zr-Si-B (at.-%) powders previously prepared ball milling for 600 min were used as starting materials. Spark plasma sintering (SPS) of mechanically alloyed Ti-Zr-Si-B powders was performed under controlled atmosphere at 1100 °C for 12 min using 20 MPa in order to obtain cylindrical bodies with 10 mm diameter. SPS samples were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and corrosion tests. The electrochemical corrosion behavior of these alloys was evaluated in electrolytic solution 1.5 SBF (Simulated Body Fluid) at 36.5 °C and pH 7.4 by means of open circuit potential (OCP) measurements and potentiodynamic polarization tests. SPS process produced dense and homogeneous samples. Despite the short sintering time, the Ti-Zr-Si-B alloys presented near-equilibrium and homogeneous microstructures. Ti6Si2B dissolving between 6.6 and 8.3 at.-% Zr was formed in the quaternary alloys with 5 and 7 at.% Zr, respectively. In detrimental to its formation, the Ti3Si phase was preferentially formed in the SPSed alloys with 10, 15 and 20 at.-% Zr, dissolving between 11.2 and 15.4, 16.9–24, and 20.6–25.3 at.-% Zr, respectively. No transpassive domain was noted in the Ti-15Zr-20Si10B alloy at higher potentials after the passive layer break occurred around the 1.44 V, which presented pits on its corroded surface in SBF medium. SPSed Ti-7Zr-20Si-10B alloy exhibited better corrosion resistance in SBF medium than the Ti pure and Ti-6Al-4V alloy.