Titanium deoxidation mechanism probed using an electron beam melting method

초록

In this study, we examine the volatilization of oxygen in titanium under electron beam melting (EBM) conditions, correlating the beam output with oxygen content changes. The potential for titanium deoxidation through the application of electron beams remains a subject of ongoing debate. To verify this experimentally, the effects of electron beam processing on the oxygen contents of different titanium raw materials are quantified by nitrogen/ oxygen analysis. Moreover, the mechanism of oxygen diffusion in titanium, which is affected by the positively charged surface layer generated by the electron beam, is evaluated by determining the corresponding activation energy using density functional theory (DFT) calculations. An average reduction of oxygen concentration by 50 % was observed following EBM. Residual gas analysis confirmed the evolution of oxygen gas over a duration of 10 min. Thermodynamic calculations indicate that deoxidation is feasible at temperatures exceeding 4,000 K in a vacuum of approximately 5 x 10- 7 Torr, thereby substantiating the potential for deoxidation. Furthermore, DFT calculations demonstrated that the oxygen diffusion coefficient increases proportionally with an increase in positive surface charge, thereby facilitating the removal of oxygen in an electron beam environment.

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