Microstructure and corrosion behavior of selective laser melting Ti-6Al-4V alloy

To reveal the feasibility of applying selective laser melting (SLM) to titanium alloy underwater equipment components, this study investigated the corrosion resistance of SLM-prepared Ti64 alloy in a simulated seawater environment. The results showed that the SLM Ti64 alloy primarily consisted of needle-like α' martensite, with a β-phase content of approximately 0.3%. Comparative electrochemical tests revealed that in a 3.5 NaCl solutionIn a 3.5% NaCl solution by mass fraction, the open-circuit potential E_ocp of SLM Ti64 alloy was −119.3 mV, significantly lower than the 234.12 mV for wroughted Ti64 alloy . Analysis of the potentiodynamic polarization curves using the extrapolation method showed that the corrosion potential E_corr of SLM Ti64 alloy was −237.3 mV, also lower than the 118.4 mV for wroughted Ti64 alloy . Fitting the impedance spectra with an equivalent circuit model, the passive film resistance R_f and charge transfer resistance R_ct of SLM Ti64 alloy were 184.1 kΩ·cm²and 2.76 × 10⁵ MΩ·cm², respectively, both lower than the 231 kΩ·cm² and 4.26 × 10⁵MΩ·cm² for wroughted Ti64 alloy . Analysis of slow strain rate stress corrosion results at different strain rates showed that the stress corrosion susceptibility of SLM Ti64 alloy was 20.2%, 17.2%, and 14.4% at strain rates of 10⁻⁵ s⁻¹, 5 × 10⁻⁶ s⁻¹ and 10⁻⁶ s⁻¹, respectively, all higher than −1.4%, 12.9%, and 10.8% for wroughted Ti64 alloy under the same conditions.