加热温度与保温时间对铝-硅镀层组织演变的影响

采用扫描电镜观察了钢板表面铝-硅镀层的微观组织,利用热模拟机研究了铝-硅镀层在不同加热温度和保温时间下镀层中合金层厚度的变化规律,利用辉光光谱仪测定了铁元素向合金层中的扩散规律。结果表明:热处理前镀层合金层组织由Fe₂Al₅二元金属间化合物和Fe₂SiAl₇三元金属间化合物组成,热处理后镀层合金层组织由Fe₂SiAl₂,Fe₂Si₂Al₅等金属间化合物组成,镀层表面生成致密的Al₂O₃膜;硅元素在合金层与镀层的交界处富集,抑制了铁元素由钢基体向镀层表面的扩散,可以有效阻止合金层厚度的进一步增加;随着加热温度升高、保温时间延长,铁元素溶出量增多,镀层表面铁质量分数达到45%~55%,导致合金层的厚度逐渐增大。

Effect of Heating Temperature and Holding time on Microstructure Evolution of Al-Si Coating

The microstructure of Al-Si coating on steel plate was observed by scanning electron microscope.The variation rule of alloy layer thickness in Al-Si coating at different heating temperature and holding time was studied by thermal simulator.The diffusion rule of iron element into the alloy layer was measured by glow spectrometer.The results show that the microstructure of alloy layer of coating is composed of Fe₂Al₅intermetallic compound and Fe₂SiAl₇ternary intermetallic compound before heat treatment.The microstructure of alloy layer of coating is composed of Fe₂SiAl₂,Fe₂Si₂Al₅and other intermetallic compounds after heat treatment,and dense Al₂O₃film is formed on the surface of coating.Silicon is enriched at the interface of alloy layer and coating layer,which inhibits the diffusion of iron element from the steel substrate to the surface of coating,and can effectively prevent the further increase of the alloy layer thickness.With the increase of heating temperature and holding time,the amount of iron element dissolved in the coating increases,and the mass fraction of iron on the surface of coating reaches 45%-55%,resulting in the thickness of alloy layer gradually increase.