GA镀层在冷轧变形下的组织形貌和耐蚀性分析

Microstructure&Corrosion Resistance Analysis of GA Coating under Cold Rolling Deformation

对铁锌合金化(Galvannealed,GA)镀层板进行冷轧变形,探究不同压下率下GA镀层的形貌、元素分布以及耐腐蚀性能的变化规律。结果表明,轧制前原始镀层主要由δ(FeZn7)和Γ(FeZn10)相组成,镀层表面存在自由Zn层,且有疏松孔洞,孔洞沿轧向变形为针状,密度逐渐减少,压下率>40%时,针状微孔洞消失。随冷轧压下率增大镀层厚度不断减薄,镀层和基体的硬度增大,较大压下率时,界面处呈现锯齿形。压下率的变化对Zn、Fe元素分布影响不大,镀层与基体界面处存在富铁扩散层;压下率>20%时,镀层发生一定破碎,界面处开始存在少量O元素;GA镀层板腐蚀失质量随着时间的增加趋于平缓,不同压下率下的GA镀层板失质量相差不大,镀层经过轧制之后仍对基体起到良好保护。

The Galvannealed(GA)-coated sheets are subjected to cold rolling deformation,and the changes in the morphology,element distribution and corrosion resistance of the GA coating at different reduction rates are explored.The results show that the original coating before rolling is mainly composed ofδ(FeZn7)andΓ(FeZn10)phases,and a free Zn layer with loose distributed holes is found on the surface of the coating.The holes are deformed into needle shape along the rolling direction,and the density gradually decreases.When the reduction rate is greater than 40%,the needle-like micro-holes disappears.With the increase of cold rolling reduction rate,the thickness of the coating layer decreases continuously,and the hardness of the coating layer and the substrate increases.When the reduction ratio is larger,the interface presents a zigzag shape.The change of reduction rate has little effect on the distribution of Zn and Fe elements,and there is an iron-rich diffusion layer at the interface between the coating and the substrate.When the reduction rate is greater than 20%,the coating is broken to a certain extent,and a small amount of O element begins to exist at the interface of the coating and the substrate.The weight loss of GA coated sheet under corrosion tends to be gentle with the increase of time,and the difference of loss weight between different reduction rates is small,and the coating after rolling still protects the substrate well.