On the Corrosion Behavior of Selective Laser-Melted Ti-6Al-4V Alloys: Role of Mesostructures, Crystallographic Texture, and Phase Fractions

The effect of microstructure on the corrosion behavior of selectively laser-melted Ti6Al4V alloys was investigated. Four different combinations of coupons were produced by varying the powder bed layer thickness, t (30 and 60 µm), and scan rotation, θ (67 and 90°). The coupons deposited using 90° scan rotation exhibit cuboidal mesostructure in contrast to the ones deposited with 67° where the grains are more equiaxed which also varies along the build and scan planes. The planes normal and parallel to the deposition direction are referred to as build (B) and scanned (S) planes, respectively. X-ray diffraction studies in conjunction with Rietveld analysis reveal that all the coupons contain a non-equilibrium martensitic phase whose volume fraction depends strongly on t and θ. Apart from this, the coupons also differ in crystallographic texture. Potentiodynamic polarization tests were conducted on 8 different samples named B3090, S3090, B6067, S6067, etc., with the prefix indicating the plane, the first two digits “t” and the next two “θ.” Among all the samples, B3090 coupons exhibit the highest corrosion rate among all the coupons owing to the high volume fraction of martensitic phase, weaker crystallographic texture, and non-equiaxed grain size.