Tailoring the microstructure and corrosion behavior of pure Ti treated by up-scaled ECAP

In this investigation, we treated commercially pure titanium (CP-Ti) using four- and eight-pass (4P and 8P, respectively) of up-scaled equal-channel angular pressing (ECAP). Subsequently, the microstructure and electrochemical behavior of the treated and untreated CP-Ti samples in a 3.5% NaCl solution were observed. Electron backscatter diffraction analysis showed that the grain dimension is reduced to about 4 μm by ECAP. Further, the percentage of low-angle grain boundaries (LAGBs) and the number of dislocations in 4P are higher than those in 8P. In addition, the recrystallized proportion in 4P is lower than that in 8P. Moreover, the basal texture is stronger in 4P than in 8P. Polarization curves revealed that the corrosion current densities of both 4P and 8P decrease in comparison to the untreated sample. Electrochemical impedance spectroscopy tests indicated that the corrosion property of CP-Ti in the 3.5% NaCl solution is improved by upscaling the ECAP, and 4P has the best anticorrosion properties. Calculations showed that a thicker protective film is developed on the surface of 4P in comparison with the virgin sample and 8P. The better corrosion resistance of 4P compared to that of 8P can be credited to the smaller grain size, greater proportion of LAGBs, and stronger basal texture.