6005A 铝合金型材搅拌摩擦焊缝的剥落腐蚀行为

The exfoliation corrosion behaviors of friction stir welding joints of 6005A aluminum alloy extrusions

摘要:

采用搅拌摩擦焊机焊接6005 A铝合金型材，获得无缺陷焊缝。借助电化学工作站、扫描电子显微镜及金相显微镜等对比研究了焊缝及母材的剥落腐蚀行为。研究结果表明，母材发生的是晶间腐蚀且部分区域发生剥落，焊缝则只发生了均匀点蚀；腐蚀评级和电化学阻抗谱都说明焊缝比母材具有更强的耐剥蚀性。通过对微观组织的对比分析，得出焊缝耐剥蚀性能提高的原因是在焊接过程中发生了动态再结晶，使母材中的带状晶粒转变成了等轴细小晶粒；同时，晶界上的第二相粒子发生固溶后，使其在晶界与晶内的分布趋于均匀从而减弱了微电偶腐蚀倾向。

Abstract:

The 6005A aluminum alloy extrusions defect-free joints were obtained by friction stir welding . By means of electrochemical workstation ,scanning electron microscope and metallographic microscope , the exfoliation corrosion properties of both 6005A aluminum’s weld-joints and base materials were investi-gated comparatively .The results showed that the pitting occured uniformly on the surface of joints ,while severe inter-granular corrosion appeared in base material and even delaminate in some parts of base materi-al .Both the rating of corrosion and electrochemical impedance spectroscopy suggested that the joints have better exfoliation corrosion resistance .Dynamic recrystallization happened in the joints during welding process ,thus making the lengthened and narrow grains being turned into equiaxed-fine ones ,meanw hile , the second-phase precipitation occured on the grain boundary ,resulting in its uniformity between grain boundary and intra-crystal ,w hich reduced the tendency of the galvanic corrosion correspondingly .