退火处理对Al/ZE42/Al复合板界面组织和腐蚀行为的影响

Influence of Annealing Treatment on Interfacial Microstructure and Corrosion Behavior of Al/ZE42/Al Composite Plate

摘要:

采用光学显微镜、扫描电镜观察显微组织、盐水浸泡测定腐蚀速率等方法，研究了退火热处理工艺对Al/ZE42/Al复合板界面微观组织以及复合板在5.0wt%NaCl水溶液中腐蚀行为的影响。结果表明：Al/ZE42/Al复合板经退火处理后，界面区域发生Mg和Al等元素的互扩散，界面扩散层包含2个反应层，靠近ZE42镁合金一侧的反应层为Mg17Al12，靠近Al板一侧的反应层为Al3Mg2金属间化合物，随退火温度的升高或者保温时间的延长，使ZE42/Al界面扩散层厚度增加，ZE42镁合金发生了再结晶组织转变；退火热处理没有改善Al/ZE42/Al复合板耐腐蚀性，提高了腐蚀速率，腐蚀机制为复合板边部向内部扩散而导致的电偶腐蚀加剧。

Abstract:

The microstructures and morphologies of Al/ZE42/Al composite plates were observed by optical microscopy (OM), scanning electron microscopy (SEM). Corrosion rates of the Al/ZE42/Al composite plates at different temperature and holding time were also measured in salt water immersion test, and the influence of annealing on interfacial microstructure of Al/ZE42/Al composite plates and corrosion behaviors in 5.0 wt% NaCl aqueous solution were investigated. The results showed that element diffusion of Mg, Al, Zn, Y and Er in Al/ZE42/Al composite plate interfacial region after annealing was occurred. The interfacial diffusion layer has two reaction layers. Mg17Al12 phase in one reaction layer near ZE42 magnesium alloy, and Al3Mg2 phase in the other reaction layer closed to Al plate. With annealing temperature and holding time increasing, the thickness of ZE42/Al interfacial diffusion layer increased, and at the meanwhile recrystallization behaviors occurred in ZE42 magnesium alloy. Annealing cannot improve corrosion resistance of Al/ZE42/Al composite plate, but improving corrosion rate. The corrosion mechanism of the Al/ZE42/Al composite plate is the aggravation of galvanic corrosion which occurred from edge to internal of the plate.