薄带铸轧凝固组织的低能晶界及遗传效应  

Low-energy grain boundaries and their hereditary effects on microstructures in strip casting

作　　者：袁国[1] 张元祥[1] 王洋[1] 方烽 李振垒[1] 王国栋[1] YUAN Guo;ZHANG Yuanxiang;WANG Yang;FANG Feng;LI Zhenlei;WANG Guodong(The State Key Laboratory of Rolling and Automation,Northeastern University,Shenyang 110819,Liaoning,China)

机构地区：[1]东北大学轧制技术及连轧自动化国家重点实验室,辽宁沈阳110819

出　　处：《钢铁》2023年第9期157-166,共10页Iron and Steel

基　　金：科技部重点研发计划资助项目(2018YFE0306102);轧制技术及连轧自动化国家重点实验室自主课题资助项目(ZZ2021006);国家自然科学基金资助项目(52104372,52001060)。

摘　　要：薄带铸轧通过水冷铜辊将液态合金直接制备成1.5~3.0 mm的薄带,具有亚快速凝固和近终成形的显著特点,能够提高液相的凝固过冷度和固-液界面处温度梯度,从而显著影响合金的组织、织构和第二相演变过程,在特种合金制备方面具有巨大的工艺潜力。通过薄带铸轧获得了Fe-Si、Fe-Ga以及Fe-Cr合金铸带,通过金相、扫描电镜(SEM)、电子背散射衍射(EBSD)和透射电镜(TEM)等技术观察凝固组织中低能量晶界的微观形貌、比例、分布等特点,并设计了模型试验验证了低能量晶界的形成原因。结果表明,Fe-Si/Cr合金在熔池大过冷度条件下通过晶粒/晶核间的界面选择作用形成Σ1/Σ3/Σ5/Σ9等特殊晶界,晶界能量等级与过冷度大小密切相关,即过冷度较大时,Σ5/Σ9等高Σ值晶界可以形成(Σ为重合位置点阵晶界的重位点阵密度),而温度升高后,能量最低的Σ1晶界比例较高。通过偏晶合金构建和复现了这种晶粒之间的界面选择作用。低能量晶界迁移速率低,可以起到稳定基体晶粒尺寸诱发异常长大的效果,所以通过工业产线获得的Fe-1.5%Si铸带实现了{100}取向晶粒异常长大,而且在轧制-退火过程中Cube得到极大强化,使得再结晶板带具有极高的横纵向磁感值。此外,这种亚快速凝固过程中特殊晶界形成机理的深度研究和物理冶金原理阐释,能够在薄带铸轧、激光增材以及粉末成形等特殊冶金过程中应用,进一步促进系列技术的进步。Thin strip casting through water-cooled copper rolls is used to directly prepare liquid alloys into 1.5-3.0 mm thin strips.This process exhibits notable characteristics of sub-rapid solidification and near-final forming,which enhances the solidification undercooling and temperature gradient at the solid-liquid interface,significantly affecting the alloy's microstructure,texture,and secondary phase evolution.Thus,this technique holds tremendous potential in the preparation of special alloys.Fe-Si,Fe-Ga,and Fe-Cr alloy strips were obtained in this research through strip casting processes.The microstructure,proportions,and distribution of low-energy grain boundaries in the solidification structure were observed using techniques such as metallography,scanning electron microscopy(SEM),electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM).Additionally,a model experiment was designed to verify the formation mechanism of low-energy grain boundaries.The results showed that under large undercooling conditions,Fe-Si/Cr alloys formed special grain boundaries such asΣ1/Σ3/Σ5/Σ9 through grain/nuclei interface selection.The energy level of grain boundaries was closely related to the degree of undercooling;higher undercooling led to the formation of highΣvalue grain boundaries likeΣ5/Σ9,while at elevated temperatures,the lowest-energyΣ1 grain boundaries became more stable.This phenomenon of grain boundary interface selection was replicated and confirmed using monotectic alloys.Low-energy grain boundaries exhibited a lower migration rate,stabilizing the size of the matrix grains and inducing abnormal grain growth.Consequently,the Fe-1.5%Si strip obtained through industrial processing achieved abnormal{100}oriented grain growth,and during the rolling-annealing process,Cube texture was significantly strengthened,resulting in a high magnetic induction value in both the transverse and longitudinal directions.Furthermore,the in-depth investigation and physical metallurgy explanation of the formation

关 键 词：薄带铸轧 近终成形 亚快速凝固 特种合金 CSL晶界 

分 类 号：TG142.1[一般工业技术—材料科学与工程] TG335.9[金属学及工艺—金属材料]