Correlation of Oxygen and Aluminum Contents of Molten Titanium-Aluminum Alloys in Alumina and Calcia Crucibles

Journal Article · Sat Jun 15 04:00:00 EDT 2019 · Metallurgical and Materials Transactions. B, Process Metallurgy and Materials Processing Science

DOI:https://doi.org/10.1007/S11663-019-01554-8· OSTI ID:22933698

Farhani, Mahdi; Hils, Gereon; Spitzer, Karl-Heinz ^[1]

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1. Clausthal University of Technology, Institute of Metallurgy (Germany)

As a key part of investigating a new proposed Ti-alloy production process, Ti-Al alloys were produced by aluminothermic reduction experiments at 1973 K in Al{sub 2}O{sub 3} crucibles. Besides, pure Ti and Al were melted inside CaO crucibles at 1973 K to investigate the possibility of melt refining in equilibrium with CaO. The experiments were carried out in a vacuum induction furnace under argon gas at atmospheric pressure. The experimental results were proved by thermodynamic evaluations including also literature data. The correlation of oxygen and aluminum in Ti melt with 11 to 23 wt pct Al in contact with Al{sub 2}O{sub 3} was assessed as 3ln X{sub O}=− 2ln X{sub Al}−9.1±0.4. This correlation in Ti melt with 3 to 10 wt pct Al in contact with CaO was 3ln X{sub O}=− 2ln X{sub Al}−14.9±0.3. Partial molar excess Gibbs free energies of mixing and combinations thereof in Ti-rich Ti-Al-O-Ca melt were assessed as RTln (γ{sub Al}{sup 2}⋅γ{sub O}{sup 3})=−894±6 (kJ/mol), RTln(γ{sub Ca}⋅γ{sub O})=−195±4 (kJ/mol), RTln γ{sub O}=−258±6 (kJ/mol), RTln γ{sub Ca}=62±7 (kJ/mol). The activity of Al{sub 2}O{sub 3} in CaO-saturated slag was assessed as 0.003 ± 0.001. The changes of Gibbs free energy for the dissolution of 1 wt pct oxygen and 1 wt pct calcium in Ti-Al melt were estimated as −630 ± 6 and −11 ± 7 (kJ/mol), respectively. A model was developed and applied to calculate the basic data for refining Ti-Al alloy.

• OSTI ID: 22933698
• Journal Information: Metallurgical and Materials Transactions. B, Process Metallurgy and Materials Processing Science, Journal Name: Metallurgical and Materials Transactions. B, Process Metallurgy and Materials Processing Science Journal Issue: 3 Vol. 50; ISSN 1073-5615; ISSN MTBSEO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM
ALUMINIUM ALLOYS
ALUMINIUM OXIDES
ARGON
ATMOSPHERIC PRESSURE
CALCIUM
CALCIUM OXIDES
CRUCIBLES
DISSOLUTION
FREE ENTHALPY
INDUCTION FURNACES
MIXING
OXYGEN
REFINING
SLAGS
THERMODYNAMICS
TITANIUM ALLOYS