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Effect of Mg Addition on Nucleation of Intra-granular Acicular Ferrite in Al-killed Low Carbon Steel |
Xiao-bing LI,Yi MIN,Zhe YU,Cheng-jun LIU,Mao-fa JIANG |
Key Laboratory for Ecological Metallurgy of Multimetallic Mineral Ministry of Education, Northeastern University,Shenyang 110819, Liaoning, China |
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Abstract To verify the formation behaviors and mechanisms of intra-granular acicular ferrite (IAF) grains nucleated by Mg-Al-O in low carbon steel, the steels containing different Mg contents were refined in a vacuum induction furnace. The effect of Mg addition on the formation of IAF structure in Al-killed low carbon steel was investigated by optical microscope (OM) and scanning electron microscope with energy dispersive X-ray spectroscope (SEM-EDX). It reveals that the IAFs are only detected in Mg-added steels, and the volume fraction of IAF increases with the Mg concentration from 8��10-6 to 26��10-6. It shows that not only the MgO-Al2O3-MnS and MgO-Al2O3-P2O5 particles are the effective nucleation sites for IAF, but also the pure MgO��Al2O3 phase can promote the ferrite nucleation. A Mn-depletion zone (MDZ) is characterized adjacent to the MgO-Al2O3-MnS, which is believed to be one of the possible mechanisms to explain the IAF nucleation. The MDZ around the MgO-Al2O3-MnS inclusion would be induced by the MnS precipitation on the inclusion. It seems that the ability of Mg-containing inclusions to induce the nucleation of ferrite might be attributed to a new mechanism, i.e., the P-rich zone formed on a few Mg-Al-O inclusions might be another factor for promoting the IAF formation.
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Received: 18 March 2015
Published: 06 May 2016
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Fund:the National Nature Science Foundation of China;the National Nature Science Foundation of China;Scientific Research Fund of Liaoning Provincial Education Department |
Corresponding Authors:
Xiao-Bing LI
E-mail: 417858881@qq.com
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