连续热浸镀Zn-Al合金镀层表面龟纹研究

Research on the Surface Moire of Coating in Continuous Hot-Dip Zn-Al Alloy

连续热浸镀锌常在锌浴中添加Al元素,以获得所需的镀层,满足工业应用。当Al含量在一定量的范围内,镀层表面出现"龟纹"(网格状)现象,影响镀层表面质量。在锌锅Al的质量分数(名义成分)为2.2%、2.4%、3.3%、4.2%、4.8%和5.2%时,连续热浸镀层均出现了龟纹。通过光学显微镜、扫描电镜能谱仪对出现龟纹的Zn-Al合金镀层表面形貌、成分和截面微观组织进行了分析。结果表明:树枝晶η-Zn相的形核和长大是形成宏观上龟纹结构的主要因素;Al含量的变化直接影响龟纹的大小,Al含量越低,龟纹越明显,Zn-2.2%Al镀层的龟纹最明显;龟纹区显微组织呈现明显地凹凸不平,其中Zn-4.8%Al龟纹区域相对比较平坦,龟纹最不明显。

Element Al is generally added in zinc bath of continuous galvanizing to get needed coating for industrial application.While the content of A1 is in a certain range,＂moire＂（ square pattern） will form on the surface of coating and affect the quality of thecoating surface.When mass fraction of Alin continuous hot-dip galvanizing bathsare（ nominal composition） 2.2%,2.4%,3.3%,4.2%,4.8% and 5.2% respectively,surface moire was appeared in the surface coating.Surface morphology,composition,macrostructure and microstructure of section of Zn-Al alloy were analyzed by Light Microscope and Scanning Electron Microscope with Energy Disperse Spectroscopy.The results indicate that; the nucleation and growth of dendriticη-Zn phase are main factors of forming moire on the macro level; Variation of A1 content directly influences length of moire,the lower of the content of A1,the more obvious of the moire,and the most obvious moire of coating is Zn-2.2% Al coating; Themicrostructure of the moire isuneven,the least obvious moire is Zn-4.8%Al which is relatively smoother than others.