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采用FE-SEM,EPMA和XRD等分析了纯锌镀层在加热过程中的组织转变和表面氧化。试验结果表明:GI镀层在较低温度加热后,厚度相对原始镀层没有改变,镀层与基板界面明显,高于800℃加热后,镀层厚度大幅增加,镀层/基体界面并不清晰;500℃加热后镀层组织为ζ相和δ相;随着加热温度升高,镀层组织转变为含铁量更高的Γ1相、Γ相和α-Fe(Zn);900℃加热后镀层几乎全为α-Fe(Zn),只在表面存在少量的Γ相;镀层中的铝随着加热温度升高逐渐向镀层表面迁移,900℃加热后铝完全迁移至镀层表面,形成连续的氧化铝层;低温加热后镀层表面只有很少的Fe-Zn相和氧化物。随着加热温度升高,表面的氧和铝含量增加,锌含量降低。900℃加热后,镀层表面存在Γ相、Al2O3和ZnO。
The microstructure and surface oxidation of pure zinc coating during heating were analyzed by FE-SEM, EPMA and XRD. The results show that after the GI coating is heated at a relatively low temperature, the thickness of the GI coating is unchanged from that of the original coating, and the interface between the coating and the substrate is obvious. When the temperature is higher than 800 ° C, the thickness of the coating increases greatly and the interface between the coating and the substrate is not clear. The microstructure of the coating was ζ phase and δ phase. With the increase of heating temperature, the microstructure of the coating turned into Γ1 phase, Γ phase and α-Fe (Zn) with higher iron content. The coatings were almost all α-Fe (Zn). Only a small amount of Γ phase existed on the surface. Aluminum in the coating gradually migrated toward the surface of the coating as the heating temperature increased. After heating at 900 ℃, the aluminum completely migrated to the surface of the coating to form a continuous layer of aluminum oxide. After low temperature heating The coating surface has very few Fe-Zn phases and oxides. As the heating temperature increases, the surface oxygen and aluminum content increases, zinc content decreased. After heating at 900 ℃, there are Γ phase, Al2O3 and ZnO on the coating surface.