中文摘要：

基于K_2ZrF_6在碱性溶液中形成负电Zr（OH）_4颗粒的作用机理,在添加K_2ZrF_6的Na_2SiO_3-KOH溶液中,对LY12铝合金表面进行微弧氧化处理.利用扫描电镜（SEM）、能谱（EDX）和X射线衍射仪（XRD）探讨了K_2ZrF_6添加剂对成膜速率、膜层形貌及结构的调制作用,并借助热阻隔性能测试评价了不同溶液中所形成膜层的热阻隔效果.结果表明,溶液中添加K_2ZrF_6增大了微弧氧化的成膜速率,使膜层的内外表面较为平整,且膜层中大尺寸缺陷减少.EDX线扫描分析表明,添加K_2ZrF_6后形成的膜层中出现大量Zr元素,且其含量随距膜/基界面距离的增加而增加.XRD结果显示,未添加K_2ZrF_6溶液制得的膜层主要由γ-Al_2O_3和α-Al_2O_3相组成;添加K_2ZrF_6后,膜层中晶态氧化物含量降低、非晶态物质增多.隔热性能测试显示,经K_2ZrF_6调制后的膜层具有更加优良的热阻隔性能.

英文摘要：

Zr（OH）_4 particle can be formed and negatively charged in alkaline solution with K_2ZrF_6 addition.Based on this mechanism,Zr-containing ceramic coatings were fabricated on LY12 aluminum alloy by microarc oxidation （MAO） using K_2ZrF_6 as a special additive in Na_2SiO_3-KOH base electrolyte.The modulation effects of K_2ZrF_6 addition on micro-microstructure,element distribution and phase composition were analyzed by SEM,EDS and XRD, respectively.Heat resistance of MAO coatings formed on LY12 aluminum alloy in different electrolyte was investigated. The results show that the K_2ZrF_6 addition can increase the micro-arc oxidation rate and significantly alter the structure of MAO coatings.Both the top surface and inner surface of MAO coatings fabricated in Zr-containing electrolyte become relatively smooth.Compared with the coating formed in Zr-free electrolyte,a large amount of Zr element is found in the coating formed in electrolyte with K_2ZrF_6 addition.Two main phases,γ-Al_2O_3 and a-Al_2O_3, are contained in Zr-free coating.In contrast,more amorphous phase is found in Zr-containing coating with reduced amount of crystalline alumina.Experimental results also demonstrate that Zr-containing coating exhibits higher heat resistance.