A Multi-step Thermodynamic Model for Alumina Formation during Aluminum Deoxidation in Fe–O–Al Melt  

作　　者：Guo-Cheng Wang Qi Wang Sheng-Li Li Xin-Gang Ai Da-Peng Li 

机构地区：[1]Key Laboratory of Chemical Metallurgy Engineering, Liaoning Province, University of Science and Technology Liaoning [2]Jiangxi University of Science and Technology [3]Benxi Steel Group Corporation

出　　处：《Acta Metallurgica Sinica(English Letters)》2015年第2期272-280,共9页金属学报（英文版）

基　　金：financially supported by the National Natural Science Foundation of China (No. 51004054);Foundation from the Liaoning Province Education Department (No. L2013127)

摘　　要：Based on the two-step nucleation mechanism, a multi-step thermodynamic model for alumina inclusion for- mation during aluminum deoxidation process was proposed in Fe-O-Al melt. Thermodynamic properties of metastable intermediates including （Al2O3）n clusters for prenucleation and α-Al2O3 nanoparticle for growth process were calculated using density functional theory. Furthermore, Gibbs free energy change of forming the intermediate by reaction between the dissolved aluminum （Al） and oxygen （O） in the melt was calculated. The results indicated that the thermodynamics of （Al2O3）n at steelmaking temperature are dependent on their structures, while that of α-Al2O3 nanoparticle are dependent on their size. The nuclei of α-Al2O3 which was originated from （Al2O3）n aggregated under a high supersaturation ratio of Al and O（Rs） in the melt. There existing excess oxygen because of the low Rs, but the secondary inclusions will be formed during the cooling process due to the excess oxygen. The nuclei lager than 20 nm can grow up spontaneously and instantaneously into primary inclusions because of thermodynamic drive. It is difficult to control the size of α-Al2O3 to be less than 20 nm, in the aluminum deoxidation process of the current conditions of steelmaking.Based on the two-step nucleation mechanism, a multi-step thermodynamic model for alumina inclusion for- mation during aluminum deoxidation process was proposed in Fe-O-Al melt. Thermodynamic properties of metastable intermediates including （Al2O3）n clusters for prenucleation and α-Al2O3 nanoparticle for growth process were calculated using density functional theory. Furthermore, Gibbs free energy change of forming the intermediate by reaction between the dissolved aluminum （Al） and oxygen （O） in the melt was calculated. The results indicated that the thermodynamics of （Al2O3）n at steelmaking temperature are dependent on their structures, while that of α-Al2O3 nanoparticle are dependent on their size. The nuclei of α-Al2O3 which was originated from （Al2O3）n aggregated under a high supersaturation ratio of Al and O（Rs） in the melt. There existing excess oxygen because of the low Rs, but the secondary inclusions will be formed during the cooling process due to the excess oxygen. The nuclei lager than 20 nm can grow up spontaneously and instantaneously into primary inclusions because of thermodynamic drive. It is difficult to control the size of α-Al2O3 to be less than 20 nm, in the aluminum deoxidation process of the current conditions of steelmaking.

关 键 词：Multi-step thermodynamics Fe-O-AI melt Aluminum deoxidation DFT Nano-α-Al2O3 

分 类 号：TF703[冶金工程—钢铁冶金]