微弧氧化处理提高AZ31B镁合金搅拌摩擦焊焊缝的耐蚀性

为提高镁合金焊接接头的耐蚀性,对6mm厚的AZ31B板材搅拌摩擦焊焊缝进行微弧氧化处理,并研究焊缝的微观组织、截面显微硬度及其微弧氧化前后的耐蚀性.结果表明:接头的微观组织明显分为3个区域:焊核区、热机械影响区及热影响区,并且接头整体硬度低于母材,焊接时焊核部位出现软化现象,导致其硬度最低.盐水浸泡实验和电化学测试表明,微弧氧化前焊缝的耐蚀性低于母材,经过微弧氧化处理后,焊缝表面形成一层致密光滑的陶瓷膜,极大提高其耐蚀性.并且,经同工艺微弧氧化处理后,焊缝表面微弧氧化膜要比母材的微弧氧化膜厚.

Improvement in corrosion resistance of friction-stir welding joint of AZ31B magnesium alloy with micro-arc oxidation treatment

In order to improve the corrosion-resistance of magnesium alloy’s welded joint,micro-arcoxidation treatment was carried out for frictionstir welding joints of AZ31B magnesium thick plate of 6 mm in thickness and the microstructure,section microhardness,and corrosion-resistance of AZ31B FSW joint before and after micro-arc oxidation treatment were investigated.The result showed that the microstructure of the welding joint could be divided into 3 remarkably different zone:nugget zone,TMAZ,and HAZ.The welded joint’s microhardness was lower than that of base metal and the microhardness of the nugget zone was the lowest due to the occurence of nugget softening during welding process.Immersion corrosion test and electrochemical test showed that the corrosion-resistance of the welding joint was lower than that of base metal.After micro-arc oxidation treatment,a dense and smooth ceramic film was formed on the welding joint and it improved the corrosion-resistance of welded joint greatly.And the coating on the friction-stir welding joint was thicker than that on base metal when the micro-arc oxidation process identical.