Si含量对热浸镀Zn-15% Al层组织的影响

Influence of Silicon Content in Hot-Dip Bath on Microstructure of Hot-Dipped Zinc-15% Aluminum Coatings

为了解合金浴中Si含量对低Al含量的热浸镀Zn-Al层组织的影响,将Q235钢浸入不同Si含量的Zn-15%Al合金浴中浸镀不同时间,制备了热浸镀Zn-15%Al层。利用扫描电镜、能谱仪等观察镀层形貌结构、分析镀层成分,研究了Si含量对镀层组织的影响。结果表明:Zn-15%Al合金镀层分为Fe-Al界面反应所形成的金属间化合物层和由富Al枝晶和枝晶富Zn相组成的自由层;少量的Si就能强烈地抑制Fe-Al反应,使化合物层减薄,并使自由层晶粒细化;随Si含量的增加,化合物层由Fe2Al5相和FeAl3相向Fe-Al-Si三元化合物4相转变;化合物层厚度随Si含量的增加总体呈减薄趋势,但略有波动;合金浴中含Si时,化合物层主要受扩散控制,其厚度呈抛物线生长规律。

Q235 steel was immersed in hot-dip bath containing different contents of Si for different durations to prepare Zn-15% Al( mass fraction; the same hereafter) alloy coatings. The morphology and microstructure of as-prepared Zn-Al alloy coatings were analyzed with a scanning electron microscope,and their elemental composition was determined with an energy dispersive spectrometer. Furthermore,the influence of Si content in the hot-dip bath on the microstructure of as-prepared Zn-Al alloy coatings was investigated. Results showed that Zn-15% Al alloy coatings consisted of intermetallic compound layer generated by Fe-Al interface reaction and a free layer composed of Al-rich dendrite and Zn-rich dendrite. Besides,even a small amount of Si was able to strongly inhibit the Fe-Al reaction,reduce the thickness of the coatings,and refine the grains in the free layer. Moreover,with the increase of Si content in the hot-dip bath,the phase constituents of the intermetallic compound layer changed from Fe 2 Al 5 and FeAl 3 to Fe-Al-Si ternary compound,while the thickness of the hot-dip Zn-Al alloy coatings tended to decline and fluctuate to some extent. Furthermore,in the presence of Si in hot-dip bath,the formation and growth of the intermetallic compound layer was dominated by diffusion process,and the variation of its thickness could be well described with parabolic curve model.