采用EBSD技术分析热浸镀铝层的显微组织

Microstructure of Hot Dipping Aluminum Coating Analyzed by Using Electron Backscatter Diffraction Technology

采用热浸镀方法在Q235钢板表面制备了镀铝层,通过扫描电镜观察了镀铝层的微观形貌,利用电子背散射衍射技术分析了镀铝层/基体界面的相分布、晶粒微观取向以及晶粒尺寸。结果表明:镀铝层的相组成包括最外层的铝和靠近基体的Fe2Al5,其中柱状Fe2Al5随浸镀时间的延长而逐渐长大;铁和铝扩散速率的不同导致镀铝层中形成一些孔洞;Fe2Al5晶粒优先选择沿着扩散方向从镀铝层表面向基体内部生长,导致镀铝层界面不均匀生长而形成舌型柱状晶;界面处基体中α-Fe的晶粒取向是随机分布的,并未受浸镀时扩散反应的影响;Fe2Al5柱状晶内部存在一些小于5°的小角度晶界;Fe2Al5晶粒的平均直径约为20μm,而基体中α-Fe的约为8μm。

The aluminum coating was prepared on Q235 steel plates by hot dipping,and the microstructure of the coating was observied by scanning electron microscopy（SEM）;the phase distribution at the coating/substrate interface,the grain orientations and the grain size were analyzed by electron backscatter diffraction（EBSD）technology.The results show that the aluminum coating consisted of an outer aluminum and Fe2Al5 adjacent to the substrate,and the tongue-like Fe2Al5 grew gradually with the increase of the dipping time;some voids were found in the coating due to the different diffusion rates between Fe and Al.Moreover,the Fe2Al5 grew preferentially along the Fe/Al inter-diffusion direction from the coating to the substrate and resulted in a non-uniform growth of the columnar Fe2Al5.However,iron grain orientation distributed randomly,which implies that the hot dipping process had no effect on the orientation.Numbers of small-angle boundaries（less than 5degrees）existed in the interior of the columnar Fe2Al5.The grain average diameter of the columnar Fe2Al5 was about 20μm and that of the iron in the substrate was about 8μm.