热镀锌DP980镀层/基板界面显微结构分析

Characterization of the coating/substrate interfacial microstructure of hot dip galvanized DP980 steel sheet

以工业生产的热镀锌双相钢DP980为研究对象,采用GD-OES分析了镀层/基板界面元素深度分布,使用SEM观察了溶锌后基板表面抑制层形貌,使用TEM观察了FIB制备的截面试样镀层/基板界面抑制层的微观结构。结果表明:镀层/基板界面上的抑制层具有两层结构,上下两层成分无明显差异,但形貌有差异。抑制层上层晶粒相对粗大、厚度较厚、且不连续;抑制层下层晶粒细小、厚度较薄、且基本连续;在上下两层抑制层之间发现基本连续的、退火时形成的Mn-Si氧化物;在热浸镀过程中,镀液中的Al、Zn和基体中的Fe同时通过氧化物层向两个相反的方向相互扩散,从而形成镀层/基板界面上两层结构的抑制层。

The microstructure of the coating/substrate interfacial layer formed on an industrially produced hot-dip galvanized dual-phase DP980 steel sheet was investigated.In-depth characterization of the inhibition layer was performed,including the alloy elemental depth profiles tested by GD-OES,the surface morphology of the substrate observed by SEM and the cross-sectional morphology revealed by FIB and TEM.The inhibition layer formed on the coating/substrate interface has a two-layer structure,which shows similar chemical composition but different morphology.The top inhibition layer which is composed of coarse grains is thick and discontinuous.The bottom inhibition layer composed of fine grains is thin and continuous.The top and bottom inhibition layers are separated by a basically continuous layer of Mn-Si external oxides formed during the annealing process.The diffusion of Al,Zn and Fe through the oxidation layer in two opposite directions occurred simultaneously during the dipping process,leading to the formation of a two-layer structure inhibition layer on the coating/substrate interface.