Material Characterization and Electrochemical Properties of Titanium Alloy 5553 Prepared by Selective Laser Melting...

The microstructure, Vickers microhardness, and electrochemical properties of an additive manufactured titanium alloy, Ti-5553 (Ti-5Al-5Mo-5V-3Cr wt %), are reported on. The alloy specimens were fabricated by selective laser melt processing. The surface morphology and electrochemical properties of the as-processed and surface-pretreated (abraded and polished) Ti-5553 specimens were investigated. The as-processed specimens had a nominal density of 4.62 ± 0.04 g/cm³. Based on comparison with the reported density for the die-cast alloy, the specimens were 99-100% dense with ca. 1% porosity. Optical microscopy and scanning electron microscopy revealed some micropores, balling features, and fusion pore defects across the surface of the alloy (XZ plane-orthogonal to the build direction). The nominal Vickers microhardness was 292 ± 2 HV. Detailed electrochemical characterization of the as-processed and surface-pretreated alloys revealed reproducible open-circuit potentials (OCPs), linear polarization resistances (R _p), and potentiodynamic polarization curves for both specimen types in naturally aerated 3.5 wt % NaCl at room temperature. For the surface-pretreated alloys, the OCP was 225 mV more noble, the anodic current in the potentiodynamic polarization curves was 72× lower, the cathodic current was 8× lower, and R _p was larger by 426× than the values for the as-processed specimens. The collective electrochemical data revealed that the surface-pretreated alloys exhibit greater corrosion resistance than the as-processed alloys due to a reduction of the real area and the formation of a more passivating oxide layer.