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Li J.,Peking University | Li J.,Aluminum Corporation of China | Zhang Z.,Peking University | Liu L.,Peking University | And 2 more authors.
ISIJ International | Year: 2013

The present paper investigated the influence of basicity and TiO2 content on the crystallization behavior of the Ti-bearing blast furnace slag (Ti-BF slag). Single Hot Thermocouple Technique (SHTT) was applied to construct the Time-Temperature-Transformation (TTT) diagrams. Scanning Electron Microscope equipped with Energy-Dispersive X-ray spectroscope (SEM-EDX) and X-Ray Diffraction (XRD) were employed to observe the morphology and determine the crystalline phase of the Ti-enriched crystals. It was found that rutile was formed as the Ti-enriched phase when the basicity of the sample was lower than 0.6, and perovskite appeared as the Ti-enriched phase with an increasing basicity to 1.0. It was also noticed that the addition of TiO2 could decrease the incubation time in the TTT diagram of the samples. The kinetics of the formation of Ti-enriched crystals, rutile and perovskite, was studied, and the mechanism of crystallization and growth was further discussed. The results indicated that the crystallization of rutile was one-dimensional interface-controlled growth, and the nucleation rate varied with the holding time at different TiO2 content. While the precipitation behavior of perovskite was three-dimensional diffusion- controlled growth, and its nucleation rate decreased with the holding time. © 2013 ISIJ.

Yan L.-M.,University of Science and Technology of China | Shen J.,General Research Institute for Nonferrous Metals, China | Li J.-P.,Aluminum Corporation of China | Mao B.-P.,General Research Institute for Nonferrous Metals, China
Rare Metals | Year: 2013

Multipass plain strain compression test of 7055 alloy was carried out on Gleeble 1500D thermomechanical simulator to study the effect of interval time on static softening behavior between two passes. Microstructural features of the alloy deformed with delay times varying from 0 to 180 s after achieving a reduction of ~52 % in the 13 stages was investigated through TEM and EBSD observations. The 14th pass of peak stresses after different delay times were gained. The peak stress decreases with the interstage delay time increasing, but the decreasing trend is gradually slower. Static recovery, metadynamic recrystallization, and/or static recrystallization can be found in the alloy during two passes. The recovery and recrystallization degree increases with longer interstage delay time. The static recovery is the main softening mechanism. Subgrain coalescence and subgrain growth together with particle-stimulated nucleation are the main nucleation mechanisms for static recrystallization. © 2013 The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg.

Zheng K.,Peking University | Liao J.,Aluminum Corporation of China | Wang X.,Peking University | Zhang Z.,Peking University
Journal of Non-Crystalline Solids | Year: 2013

Raman spectra of CaO-MgO-SiO2-TiO2 slags were carefully analyzed to obtain the effect of TiO2 on the slag structures and the results are important for a better understanding of the behaviors of Ti-bearing slags. Gaussian deconvolutions of the Raman curves provide us with a deep insight into various structural units of the slags. The silicate network was more polymerized because of the increase of TiO 2. Q2 (silica tetrahedra with two bridging oxygens) and Q3 species increase at the cost of Q0 and Q1 species. A significant fraction of Ti4 + plays the role of network formers and enters the silicate network, while some other Ti4 + exist in the slags in the form of TiO44 - monomers suggested by ~ 790 cm- 1 bands. A small content of 6-coordinated Ti4 + occurs when the fraction of TiO2 is relatively high. 5-Coordinated Ti4 + indicated by 870 cm- 1 may also appear and help the initial addition of Ti4 + into silicate network. © 2013 Elsevier Ltd. All rights reserved.

Sun Y.,Peking University | Zheng K.,Peking University | Liao J.,Aluminum Corporation of China | Wang X.,Peking University | Zhang Z.,Peking University
ISIJ International | Year: 2014

This study provided a fundamental analysis of the viscosity and structure of titanium bearing blast furnace slags modified by different levels of P 2O5 addition. The viscosity of slag melts was obtained by rotating cylinder method, which is a significant factor for blast furnace process and utilization of slags. The results showed that the slag viscosity was greatly influenced by basicity. Slag viscosity decreased and the calculated apparent activation energy for viscous flow also decreased with increasing basicity, which indicated the breakdown of melt structure. The addition of P2O5 substantially increased the slag viscosity at each basicity, and the increasing trend was most pronounced at basicity 0.5. To connect the viscosity changes of slags to the slag melt structure, Fourier transformation infrared (FTIR) and Raman spectral spectroscopy analysis were performed in this study. FTIR results clearly indicated that the added P 2O5 increased the degree of polymerization of slags, corresponding to the increase of slag viscosity. Based on Raman and FTIR curves, it can be concluded that P2O5 acted as a characteristic network former in the melts. © 2014 ISIJ.

Wu J.,Tsinghua University | Wan H.,Aluminum Corporation of China | Chen W.,Tsinghua University | Shi L.,Tsinghua University
Qinghua Daxue Xuebao/Journal of Tsinghua University | Year: 2010

The energy consumption and greenhouse gas emissions of the primary aluminum industry in China were quantified to give a more complete understanding of the Chinese primary aluminum industry, based on the methodology given by the International Aluminum Institute. The results show that in 2005, the Chinese primary aluminum industry consumed 65.78 Mt of standard coal, which accounted for 2.9% of the national total energy consumption which aluminum smelting consumed 67.7% of the total energy consumption and discharged 82.7% of the greenhouse gases in the industry. Electricity contributed 71.9% of the total energy consumption and 69.2% of the greenhouse gas emissions for the primary aluminum production. Thus, improving the electricity production structure can effectively reduce energy consumption and greenhouse gas emissions.

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