冷却速率和稀土含量对Zn-Al-Mg合金组织和耐蚀性能的影响  

Effect of cooling rate and rare earth content on microstructure and corrosion resistance of Zn-Al-Mg alloys

作　　者：徐呈亮 刘广会 刘武华[2] 蒋光锐 李研 滕华湘 XU Chengliang;LIU Guanghui;LIU Wuhua;JIANG Guangrui;LI Yan;TENG Huaxiang(Research Institute of Technology,Shougang Group Co.,Ltd.,Beijing 100043,China;Shougang Jingtang United Iron and Steel Co.,Ltd.,Tangshan 063200,China)

机构地区：[1]首钢集团有限公司技术研究院,北京100043 [2]首钢京唐钢铁联合有限责任公司,河北唐山063200

出　　处：《轧钢》2024年第3期53-63,共11页Steel Rolling

基　　金：河北省重大科技成果转化专项项目(22281001Z)。

摘　　要：为探究不同冷速条件下稀土元素对Zn-Al-Mg合金镀层的作用机理,以细化镀层组织、提升耐蚀性能,利用热力学计算、扫描电镜(SEM)、X射线衍射分析(XRD)及电化学测试方法对Zn-1.7%Al-1.1%Mg合金在不同冷速(空冷、水冷、炉冷)及不同La、Ce稀土元素含量条件下的凝固组织和耐蚀性能进行了系统研究。结果表明:运用热力学计算方法可以预测不同Ce含量Zn-Al-Mg合金在凝固过程中的析出相及对应的析出序列;对于不同La、Ce含量Zn-Al-Mg合金最先凝固生成LaZn_(13)/CeZn_(11)初晶相,之后依次生成富锌相、Mg_(2)Zn_(11)/MgZn_(2)相和富铝相。随着冷却速率的增加,合金的凝固组织变得更为细小,且凝固组织中的Mg_(2)Zn_(11)相逐渐转变为MgZn_(2)相。这是因为当凝固速率增大时,在Zn-Al-Mg合金体系中会发生Mg_(2)Zn_(11)←→MgZn_(2)的亚稳相转变。Tafel极化曲线测试和交流阻抗图谱测试(EIS)结果表明:当合金中稀土含量增加时,合金的耐蚀性有一定程度的提升;而当冷速增大时,其耐蚀性能有着较为明显的提升。细小的显微组织有利于提升合金的耐蚀性,故冷却速率仍是决定合金耐蚀性能的主要控制参数。In order to refine the microstructure and improve corrosion resistance,the influence of cooling rate on the Zn-Al-Mg alloys with different rare earth contents were theoretically investigated.The solidified microstructures and corrosion resistance of the La and Ceadded Zn-1.7%Al-1.1%Mg alloys were studied under different cooling rates(air cooling,water cooling,furnace cooling)and varied rare earth contents,and thermodynamic calculations,scanning electron microscopy(SEM),X-ray diffraction method(XRD)and electrochemical test were carried out in the present work.The results show that the thermodynamic calculations can predict the precipitated phases and the related precipitation sequence of the Ce-added Zn-Al-Mg alloys during the solidification process.The LaZn_(13)/CeZnu primary phases were initially precipitated from the La and Ce added Zn-Al-Mg molten alloys,and the Zn-rich phase,Mg Zn_(11)/MgZn_(2) phases and Al-rich phase were solidified from the molten alloys,respectively.With the increase of the cooling rate,more fined microstructures were obtained and the Mg,Znu phase would turn into MgZn_(2) phase.The reason lies on that the metastable phase transition Mg_(2)Zn_(11)←→MgZn_(2) takes place in the Zn-Al-Mg system when the cooling rate increases.The results of Tafel polarization test and electrochemical impedance spectroscopy test(EIS)show that with the increase of rare earth contents,the corrosion resistance of the alloys elevates to a certain extent.When the cooling rate increases,the corrosion resistance of the Zn-Al-Mg alloys can be improved prominently.It can be concluded that refined microstructure benefits to the increase of corrosion resistance,thus cooling rate acts as the main controlling parameter of the alloy corrosion resistance of the alloy.

关 键 词：Zn-Al-Mg合金 凝固组织 耐蚀性 冷却速率 微量稀土La、Ce元素 

分 类 号：TG174.4[金属学及工艺—金属表面处理]