采用高温共聚焦激光显微镜(CSLM)对含Ti复合夹杂物诱导晶内针状铁素体(IAF)进行动态原位观察, 并用OM, FE-SEM, EDS和EPMA研究奥氏体晶粒尺寸和冷却速率对含Ti复合夹杂物诱导生成IAF的影响. 结果表明, IAF的开始生成温度随奥氏体晶粒尺寸的增加,先升高后降低; 生成IAF体积分数随冷却速率的提高显著增加, 归功于IAF开始生成温度的提高. 贫Mn区的形成是含Ti复合夹杂物(Ti-Mn-O)+(Si-Al-Mn-O)+MnS诱导生成IAF的主要驱动力. 此外, 在该实验条件下得出, 当奥氏体晶粒尺寸在132-255 μm时, IAF开始生成的温度范围为550-633℃;奥氏体晶粒尺寸为176 μm, 冷却速率为5℃/s时, 室温组织中IAF体积分数高达90%.
The nucleation of intragranular acicular ferrite (IAF) on complex titanium–containing inclusions for titanium deoxidized steel was observed dynamically by confocal scanning laser microscope (CSLM), and the effects of average austenite grain size and cooling rate on the nucleation of IAF was systematically investigated by using OM, FE–SEM and EDS. Furthermore, the mechanism of IAF nucleation on the complex titanium–containing inclusions was studied by using EPMA in detail. The results show that the starting formation temperature of IAF firstly increases with increasing austenite grain size, then decreases. With the increase of cooling rate, the volume fraction of IAF increases obviously due to the increase of the starting formation temperature. Mn–deplete zone (MDZ) is considered to be a dominant driving force for the nucleation of IAF. In addition, it is found that the range of starting formation temperature of IAF is 550—633 ℃ with austenite grain size in the range of 132—255 μm. Volume fraction of IAF obtained at room temperature is up to 90% with austenite grain size of 176 μm and a cooling rate of 5 ℃/s in this experiment condition.
[1] Mabuchi H, Uemori R, Fujioka M. ISIJ Int, 1996; 36: 1406
[2] Koseki T, Thewlis G. Mater Sci Technol, 2005; 21: 867
[3] Zhang D, Terasaki H, Komizo Y. Acta Mater, 2010; 58:1369
[4] Smith Y E, Coldren A P, Cryderman R L. Toward Improved Ductility and Toughness. Tokyo: Climax Molybdenum Company Ltd., 1972: 119
[5] Takamura J C, Mizoguchi S. Proc 6th Int Iron and Steel Congress, Janpan, 1990(CD–Rom)
[6] Yamada W, Matsumiya T. Proc 6th Int Iron and Steel Congress, Janpan, 1990(CD–Rom)
[7] Kikuchi N, Nabeshima S, Kishimoto Y, Ishiguro Y, Sridhar S. ISIJ Int, 2009; 49: 1036
[8] Byun J S, Shim J H, Cho Y W, Lee D N. Acta Mater, 2003; 51: 1593
[9] Yang C W, Jiang M, Hu Z Y, Lu N B, Wang X H. AISTech 2011 Proceedings, USA: The Association for Iron & Steel Technology, 2011: 661
[10] Yin H B, Shibata H, Emi T, Suzuki M. ISIJ Int, 1997; 37: 936
[11] Sarma D S, Karasev A V, Jonsson P G. ISIJ Int, 2009; 49: 1063
[12] ShuW, Wang X M, Li S R, He X L. Acta Metall Sin, 2010; 46: 997
(舒玮, 王学敏, 李书瑞, 贺信莱. 金属学报, 2010; 46: 997)
[13] Yang Z, Wang F, Wang S, Song B. Steel Res Int, 2008; 79: 390
[14] Ohkita S, Horii Y. ISIJ Int, 1995; 35: 1170
[15] Ricks R A, Howell P R, Barritte G S. J Mater Sci, 1982; 17: 732
[16] Jin H H, Shim J H, Cho Y W, Lee H C. ISIJ Int, 2003; 43: 1111
[17] Brooksbank D, Andrews K J. Iron Steel Inst, 1972; 210: 246
[18] Shim J H, Oh Y J, Suh J Y, Cho Y W, Shim J D, Byun J S, Lee D N. Acta Mater, 2001; 49: 2115
[19] Shim J H, Cho Y W, Chung S H, Shim J D, Lee D N. Acta Mater, 1999; 47: 2751
[20] Byun J S, Shim J H, Suh J Y, Oh Y J, Cho Y W, Shim J D, Lee D N. Mater Sci Eng, 2001; A319–321: 326
[21] Ishikawa F, Takahashi T, Ochi T. Metall Mater Trans, 1994; A25: 929
