title: Thermodynamic Destabilization of Ti-O Solid Solution by H2 and Deoxygenation of Ti Using Mg.
abstract: Reactive metals including Ti, Zr, Hf, and V, among others, have a strong chemical affinity to oxygen, which makes them difficult to produce and costly to use. It is especially challenging to produce pure or metal alloy powders of these elements when extremely low oxygen content is required, because they have high solubility for oxygen, and the solid solution of these metals with oxygen is often more stable thermodynamically than their oxides. We report a novel thermochemical approach to destabilize Ti(O) solid solutions using hydrogen, thus enabling deoxygenation of Ti powder using Mg, which has not been possible before because of the thermodynamic stability of Ti(O) solid solutions relative to MgO. The work on Ti serves as an example for other reactive metals. Both analytical modeling and experimental results show that hydrogen can indeed increase the oxygen potential of Ti-O solid solution alloys; in other words, the stability of Ti-O solid solutions is effectively decreased, thus increasing the thermodynamic driving force for Mg to react with oxygen in Ti. Because hydrogen can be easily removed from Ti by a simple heat treatment, it is used only as a temporary alloying element to destabilize the Ti-O systems. The thermodynamic approach described here is a breakthrough and is applicable to a range of different materials. This work is expected to provide an enabling solution to overcome one of the key scientific and technological hurdles to the additive manufacturing of metals, which is emerging rapidly as the future of the manufacturing industry.
authors.affiliation: Department of Metallurgical Engineering, University of Utah , Salt Lake City, Utah 84112, United States.|Institute of Process Engineering, Chinese Academy of Sciences , Beijing 100190, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Metallurgical Engineering, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: Zhigang Zak
authors.initials: ZZ
authors.lastname: Fang
authors.affiliation: Department of Metallurgical Engineering, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: Pei
authors.initials: P
authors.lastname: Sun
authors.affiliation: Department of Metallurgical Engineering, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: Tuoyang
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Department of Metallurgical Engineering, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: Yang
authors.initials: Y
authors.lastname: Xia
authors.affiliation: Department of Metallurgical Engineering, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: Chengshang
authors.initials: C
authors.lastname: Zhou
authors.affiliation: Department of Metallurgical Engineering, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Huang