Determination of the oxygen removal limits from Ti and Ti-6Al-4V by the hydrogen-assisted Mg deoxygenation method

Deoxygenation is in high demand in the titanium industry. This research was carried out to experimentally determine the oxygen removal limits by the novel hydrogen-assisted Mg deoxygenation method. Spherical Ti and Ti-6Al-4V (or TC4, Ti64) powders with around 2.2 wt% oxygen were prepared for the deoxygenation research. The deoxygenation kinetics were modeled based on a non-steady-state radial diffusion. There-sults show that in the beta phase region, the time to reach the equilibrium is slightly affected by the initial oxygen content in titanium, but is strongly influenced by the particle size. The reliance of the equilibrium duration on the diffusion coefficient is stronger when the particle size is larger. Guided by the kinetic prediction, deoxygenation experiments were carried out. Under a 1 atm pure H2 atmosphere, the deoxygenation limits by Mg for pure Ti are 252 ppm at 700 & DEG;C, 289 ppm at 750 & DEG;C, and 554 ppm at 800 & DEG;C, and for TC4 are 296 ppm at 750 & DEG;C, 371 ppm at 800 & DEG;C, and 743 ppm at 850 & DEG;C, consistent with the thermodynamics that a lower temperature possesses a more potent driving force for deoxygenation. These data have clearly demonstrated the strong deoxygenation capability of the hydrogen-assisted Mg deoxygenation method.(C) 2022 Elsevier B.V. All rights reserved