Comparison of deoxidation capability of solid solution and intermetallic titanium alloy powders deoxidized by calcium vapor

A comparison of the deoxidation capability of solid solution and intermetallic titanium alloy powders deoxidized by calcium vapor was investigated. The oxygen concentration of Ti-6Al-4V, Ti-27Nb, Ti-42Nb, Ti-35V-15Cr, Ti-25Fe-5Al, and Ti65Fe35 alloy powders before deoxidation were 2,610 ppm, 3,300 ppm, 3,780 ppm, 5,880 ppm, 1,725 ppm, and 4,635 ppm, respectively. After deoxidation, the oxygen concentration of the Ti-6Al-4V, Ti-27Nb, Ti-42Nb, and Ti-35V-15Cr solid-solution alloy powders were 355 ppm, 210 ppm, 330 ppm, 95 ppm, respectively, while the Ti-25Fe-5Al and Ti65Fe35 intermetallic alloy powders were 385 ppm and 1250 ppm, respectively. Compared with the oxygen concentration before deoxidation, the solid-solution Ti alloy powders showed a high oxygen reduction rate of approximately 80% or more, while the intermetallic Ti alloy powders showed a lower oxygen reduction rate of approximately 70%. Based on the theoretical deoxidation limit of pure Ti and the actual deoxidation result of pure Ti powder, solid-solution Ti alloy powders have reduced oxygen solubility due to the addition of alloying elements, resulting in reduced oxygen concentration after deoxidation. However, the intermetallic Ti alloy powders showed a difference in oxygen concentration among them due to the effect of TiFe intermetallic phase with high equilibrium oxygen concentration in the deoxidation reaction. (C) 2020 Elsevier B.V. All rights reserved