热镀锌钢板镀层合金化过程铁-锌相变的原位观察

In-situ observation on microstructure evolution of galvanized coating during galvannealing

用ESEM原位观察了铝含量不同的两种热镀锌钢板合金化过程中镀层表面和断面铁-锌合金相的生长,并用GDOES分析了镀层中元素分布和相结构的变化。实验结果表明:铝含量对热镀锌钢板合金化过程中镀层结构的变化具有重要的影响。铝含量为0.13%时,镀层从ζ相的形成到转变为δ相的过程是均匀进行的,铁-锌合金相均匀地生长,镀层的相结构以δ相为主;铝含量为0.22%时,界面处的铁-锌反应不能同时进行,合金化过程局部被延迟,镀层中形成了大量的暴发组织,ζ相及δ相的形成时间不同且不能均匀有序地形成,镀层的相结构是δ和ζ相的混合物。

Formation of Fe-Zn intermetallic compounds in hot-dip galvanizing coatings with different contents of aluminum was investigated by in-situ observation on an environmental scanning electron microscope（ESEM）.Distribution of elements and phase evolution in the coatings were investigated by glow discharge optical emission spectroscopy（GDOES）.The results show that the aluminum content in the galvanizing layer had a strong influence on microstructure of the coatings in the process of galvannealing.When the content of aluminum is 0.13% in the galvanizing coating,the process of decomposition of ζ phase into δ phase in the coatings is uniformly carried out,the formation of Fe-Zn intermetallic compounds is uniform and the microstructure of the galvannealed coating is mainly composed of δ phase.When the content of aluminum is 0.22% in the galvanizing coating,the Fe-Zn intermetallic phase at the interface between the coating and steel substrate is not uniformly formed,and the formation of Fe-Zn intermetallic phase is delayed at some locations and the phase is formed rapidly at other locations.In the galvannealed coating,the ζ phase and δ phase are not formed simultaneously and uniformly,the microstructure of galvannealed coatings consists of δ phase and ζ phase.