Corrosion behavior of nano/sub-micron F401 titanium alloy

Titanium alloys are attractive as structural materials mainly due to their high specific strength and excellent corrosion resistance. Modifying conventional Ti alloys to impart nanostructural features holds promise for improving specific strength without reducing corrosion resistance. This study aimed to evaluate the corrosion behavior of a nano/sub-micron F401 titanium alloy compared to its conventional Ti-6Al-4V counterpart. Following mechanical alloying and extrusion, the microstructure was evaluated using optical microscopy, SEM, HRSEM, and X-ray diffraction analysis. Mechanical properties were evaluated by tension and micro-hardness tests. The corrosion behavior was examined by an immersion test, salt spray testing, and potentiodynamic polarization analysis. Stress corrosion resistance was evaluated by slow strain rate testing (SSRT) in terms of UTS and time to failure versus strain rate. All the corrosion tests were carried out in 3.5% NaCl solution apart from the salt spray testing, which was done in 5% NaCl solution. The results indicate that the corrosion resistance of the novel F401 alloy was not different from its Ti-6Al-4V counterpart, although the mechanical strength was improved. Thus, the grain refinement in the F401 alloy increased the mechanical strength, whereas neither the grain refinement nor the porosity acquired during the preparation process impaired the excellent corrosion resistance. Modifying conventional Ti alloys to impart nanostructural features holds promise for improving specific strength. Here, we show that grain refinement in an F401 alloy increases the mechanical strength without impairing the excellent corrosion resistance, relative to the conventional Ti-6Al-4V alloy.