Corrosion behavior of Ti-6Al-4V alloy welded by scanning electron beam

The corrosion behavior of Ti-6Al-4V alloy welded by SEE (scanning electron beam) is described in this paper. Solidification macrostructure of weld was transformed from 650-mu m columnar crystals to 100-mu m equiaxed crystals by SEE. Anodic polarization behavior of the weld was different following the change in solidification macrostructure. Anodic polarization curve of 150-mu m equiaxed-grain weld coincided with that of base metal, which indicated a best state of equal corrosion tendency between the base and the weld metal. Alloy element homogeneity in the equiaxed solidification structures made the weld more corrosion resistant than the columnar solidification structures. Fine microstructure and a small quantity of dislocations have a good effect on uniform corrosion resistance of the weld, but coarse microstructure, a spinodal decomposition of the metastable beta-phase and a large quantity of dislocations were related to the inferior resistance either to uniform corrosion or to local corrosion. (C) 2000 Elsevier Science S.A. All rights reserved.