材料期刊网

占空比是微孤氧化过程中的重要参数,目前研究多针对恒定单一占空比模式.为此,在优化的复合电解液体系中对ZK60镁合金进行微弧氧化处理,研究微弧氧化过程中阶段调节不同占空比对微弧氧化膜层性能的影响.通过电压-时间曲线分析微弧氧化膜层生长特性,并利用扫描电镜(SEM)、激光共聚焦显微镜、全浸试验等手段对膜层微观结构及性能进行表征.结果表明:阶段调节占空比模式下,微弧氧化初期应采用较大占空比有利于钝化膜击穿,微弧氧化中期适当降低占空比有利于膜层平稳生长,膜层生长后期采用较小占空比可以较好地修复膜层;当阶段占空比参数设置为60％-50％-40％时,膜层微观结构均匀致密,在3.5％溶液中室温浸泡120 h后的腐蚀速率为0.100 7g/(m2·h),表现出良好的耐蚀性;膜层与基体结合牢固,其最高临界载荷为8.95 N.

Micro-arc oxidation(MAO) process was carried out on the surface of ZK60 magnesium alloy in an optimized dual electrolyte system,and the influences of steps duty ratio regulated during MAO process on the performance of MAO coating were analyzed.The growth characteristics of MAO coating was investigated by voltage-time curves,and the microstructure and properties of MAO coating were evaluated by scanning electron microscope(SEM),laser confocal scanning microscope and immersion test.Results showed that under steps duty cycle mode,a higher duty cycle applied on the initial process of MAO was beneficial to the breakdown of passive layer.In the middle stage of MAO process,silight decline of duty cycle could promote stable growth of MAO coating.In the last stage of MAO process,the duty ratio should switch smaller for repairing coating better.Therefore,when steps duty ratio was set to 60％-50％-40％,the prepared coating possessed uniform and compact structure,and the corrosion rate of coating was 0.100 7 g/(m2 · h) in 3.5 ％ NaCl solution for 120 h,which performed excellent corrosion resistance.In addition,the prepared coating had good combination with the substrate,and the maximum critical load was 8.95 N.