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.