The effects of cooling rate on acicular ferrite (AF) nucleation, growth, and inclusion characteristics in Ti-Zr deoxidation steel were studied by utilizing the high temperature confocal laser scanning microscope (HT-CLSM). The results indicated that with the increase of cooling rate, the ferrite start nucleation temperature decreased, and the difference of first nucleation temperature between AF and ferrite side plate (FSP) reduced. When the cooling rate increased to 10.0 °C/s, AF and FSP simultaneously nucleated at 564.5 °C. In addition, the AF actual growth rate rose with the increase of cooling rate and reached 30.13 µm/s at 10.0 °C/s cooling rate. The AF ratio in microstructure increased first and then decreased with the cooling rate increase and was up to the maximum 45.83 pct at 1.0 °C/s cooling rate. For inclusion characteristics, cooling rates had no obvious effect on inclusion types, but had a great influence on inclusions size distribution. With the cooling rate increase, the inclusion average diameter reduced, and diminished to 1.39 µm at 10.0 °C/s cooling rate. Finally, the AF nucleation on the Ti-Zr-Mn-O-S + TiN inclusion could be explained by the low lattice misfit between ferrite and TiN that precipitated on the Ti-Zr-Mn-O-S inclusion surface.

中文翻译：

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Ti-Zr脱氧钢不同冷却速度下针状铁素体形核和生长的原位观察

利用高温共聚焦激光扫描显微镜(HT-CLSM)研究了冷却速度对Ti-Zr脱氧钢针状铁素体(AF)形核、生长和夹杂物特性的影响。结果表明，随着冷却速度的增加，铁素体开始成核温度降低，AF与铁素体侧板（FSP）的首次成核温度差异减小。当冷却速度增加到 10.0 °C/s 时，AF 和 FSP 同时在 564.5 °C 成核。此外，AF实际增长率随着冷却速度的增加而上升，在10.0°C/s的冷却速度下达到30.13 µm/s。显微组织中的AF比随着冷却速度的增加先增加后下降，在1.0℃/s的冷却速度下达到最大值45.83%。对于包含特性，冷却速度对夹杂物类型没有明显影响，但对夹杂物尺寸分布有很大影响。随着冷却速度的增加，夹杂物平均直径减小，并在 10.0 °C/s 的冷却速度下减小到 1.39 µm。最后，Ti-Zr-Mn-OS + TiN 夹杂物上的 AF 形核可以用铁素体和 TiN 之间的低晶格错配来解释，这些错配在 Ti-Zr-Mn-OS 夹杂物表面沉淀。