Study of the kinetics of austenite grain growth by dynamic Ti-rich and Nb-rich carbonitride dissolution in HSLA steel: In-situ observation and modeling
Study of the kinetics of austenite grain growth by dynamic Ti-rich and Nb-rich carbonitride dissolution in HSLA steel: In-situ observation and modeling
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HSLA 钢中富钛和富铌碳氮化物动态溶解的奥氏体晶粒长大动力学研究：原位观察和建模
DOI：
10.1016/j.matchar.2020.110612
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发表时间：
2020-11-01
影响因子：
4.7
通讯作者：
Li, Huijun
中科院分区：
文献类型：
--
作者：
Zhang, Yang;Li, Xiaohua;Li, Huijun
通过显微组织分析和高分辨扫描电镜分析，研究了碳氮化物对低合金高强钢奥氏体晶粒长大的影响。利用高温激光扫描共聚焦显微镜原位测量了不同温度下奥氏体晶粒的长大。在不同温度下的微晶化样品中观察到两种不同形貌的析出物，其中含有大量的Ti和Nb。较小的富Nb球形碳氮化物在较高温度下溶解，而较大的富Ti矩形碳氮化物具有较高的热稳定性，并且可以钉扎在奥氏体晶界上。本研究揭示了Nb在奥氏体中的溶解引起奥氏体晶粒的快速长大，减缓铁素体相变，有利于贝氏体的形成。提出了一个考虑不同类型碳氮化物动态溶解的奥氏体长大动力学模型。模型的结果显示出与实验结果相同的总体趋势，并且可以解释个体差异。该模型可用于预测低合金高强度钢奥氏体化过程中的晶粒尺寸，并能较连续地反映奥氏体晶粒在整个过程中的变化。
The effect of carbonitrides on the growth of austenite grains in high-strength low-alloy (HSLA) steel was investigated through microstructure analysis and high-resolution dilatometry. The austenite grain growth at various temperatures was measured in situ using high temperature laser scanning confocal microscopy. Two kinds of precipitates with different morphologies containing large amounts of Ti and Nb were observed in the austenitized samples at different temperatures. The smaller Nb-rich spherical carbonitrides dissolved at the higher temperature, while the lager Ti-rich rectangular carbonitrides have a higher thermal stability and can pin at the austenite grain boundary. This study reveals that the dissolution of Nb in austenite causes the rapid growth of austenite grains and slows down the ferrite phase transition, which is beneficial to the formation of bainite. A kinetic model of austenite growth considering the dynamic dissolution of different types of carbonitrides is proposed. The results of the model show the same overall trend as the experimental results, and the individual differences can be explained. The proposed model can be used to predict the austenite grain size during the austenitizing process of HSLA steel and can reflect the austenite grain change throughout the process more continuously.