低碳微合金钢晶界铁素体三维形态及形成机理  

Three-dimensional morphology and formation mechanism of grain boundary ferrite in low carbon microalloyed steel

作　　者：曹胜利 武绍文 张彩军 张庆军 CAO Sheng-li;WU Shao-wen;ZHANG Cai-jun;ZHANG Qing-jun(College of Metallurgy and Energy,North China University of Science and Technology,Tangshan 063210,Hebei,China;Hebei Province High Quality Steel Continuous Casting Engineering Technology Research Center,Tangshan 063210,Hebei,China;Comprehensive Testing and Analyzing Center,North China University of Science and Technology,Tangshan 063210,Hebei,China;State Key Laboratory of Advanced Metallurgy,University of Science and Technology Beijing,Beijing 100083,China)

机构地区：[1]华北理工大学冶金与能源学院,河北唐山063210 [2]河北省高品质钢连铸工程技术研究中心,河北唐山063210 [3]华北理工大学综合测试分析中心,河北唐山063210 [4]北京科技大学钢铁冶金新技术国家重点实验室,北京100083

出　　处：《钢铁》2022年第3期124-132,共9页Iron and Steel

基　　金：国家自然基金资助项目(51974130,5217042024,51874137);河北省自然科学基金-钢铁联合研究基金资助项目(E2020209044)。

摘　　要：为了更好地研究低碳微合金钢晶界铁素体的三维形态及形成机理,利用配有电子背散射衍射(EBSD)的聚焦离子束场发射扫描电子显微镜构建了低碳微合金钢不同析出位置的晶界铁素体三维形貌,通过高温激光共聚焦显微镜原位观察技术计算了晶界铁素体在试验条件下的生长速率,最后利用Matlab建立了试样钢成分下不同温度下溶质元素的扩散模型,从试验结果和理论数据两方面进行了论证与分析。研究发现,晶界面铁素体并非沿着奥氏体母相晶粒生长,而是以一定角度长向晶内,同时只是在奥氏体晶界附近生长,不能生长到太深的位置,其三维形貌正面为扁平状,侧面呈细长条状,伴随着大量凹坑和缺陷;晶界棱铁素体一侧与奥氏体界面固定,尾部较宽呈尖角状向晶内生长,其三维形貌形如具有尖顶的三棱锥状,附着面平滑、整齐,侧面存在很深沟壑。利用原位观察技术计算发现,温度区间在725~775℃析出的晶界铁素体之间生长速率较快,为100~250μm/s,在其余温度区间析出的晶界铁素体生长速率较小。试验测得晶界铁素体的生长速率随温度的变化在局部平衡/准平衡模式下的分布,发现该钢种的晶界铁素生长主要分布在准平衡模式,晶内铁素体的生长速率只受碳的扩散控制。In order to better understand the three-dimensional morphology and formation mechanism of grain boundary ferrite in low carbon microalloyed steel,the 3D morphology of the different location was observed by focused ion beam scanning electron microscope equipped with electron back-scatter diffraction(EBSD),and the growth rate under test conditions was calculated by in-situ observation technology,finally the solute diffusion model was calculated by Matlab,from two aspects of test results and the theoretical data for the demonstration and analysis.The results show that the grain boundary surface ferrite does not grow along the austenite parent phase grain,but grows in a certain angle toward the grain.At the same time,it only grows near the austenite grain boundary and cannot grow too deep.Its three-dimensional morphology is flat on the front and thin strip on the side,accompanied with a large number of pits and defects.The grain boundary ribbed ferrite and austenite at the grain boundary have fixed interface on one side,and the other side is angular and grows into the grain.The three-dimensional morphology of ridged ferrite is like a triangular pyramid with a pointed tip.The adhesion surface is smooth,tidy,and the side has a deep gully.The findings were calculated using in situ observation techniques,the grain boundary ferrite precipitated at 725-775 ℃ has a faster growth rate,Locating between 100-250 μm/s,and the grain boundary ferrite precipitated at other temperatures has a lower growth rate.The distribution of grain boundary ferrite growth rate with temperature in local equilibrium/para-equilibrium mode is obtained,the results find that the growth rate of grain boundary ferrite is mainly distributed in the para-equilibrium mode,and the growth rate of intragranular ferrite is only controlled by carbon diffusion.

关 键 词：晶界面铁素体 晶界棱铁素体 三维形貌 析出位置 溶质扩散模型 

分 类 号：TG142.33[一般工业技术—材料科学与工程]