微弧氧化膜对7A52铝合金搅拌摩擦焊接头腐蚀不均匀性的影响

Influence of micro-arc oxidation film on corrosion of inhomogeneity of 7A52 aluminum alloy friction stir welding joint

7A52铝合金搅拌摩擦焊接头焊核区由于发生动态再结晶,晶粒比较细小,组织呈现"洋葱环"分布,热力影响区的组织沿塑性流动方向分布,热影响区晶粒尺寸发生了明显的长大.接头组织不均匀导致不同区域的腐蚀行为不同.结果表明,没有微弧氧化膜时,母材的致钝电流远小于焊核区及热(力)影响区,更容易钝化;当微弧氧化膜的厚度为50μm,母材的致钝电流小于焊核区及热(力)影响区,较薄的微弧氧化膜对接头腐蚀不均匀性的改善作用不明显;当微弧氧化膜的厚度为70μm时,接头不同区域钝化特征接近,微弧氧化膜有助于减小接头组织不均匀对接头不同区域的腐蚀不均匀的影响.

Due to dynamic recrystallization of the 7A52 aluminum alloy friction stir welding joint weld zone.The grain size is relatively small,the organization presents“onion ring”distribution.the thermo mechanically affected zone is distributed along the plastic flow direction,and the grain size of the heat affected zone is obviously grown.The unevenness of the joint structure leads to different corrosion behaviors in different regions.The results show that when there is no micro-arc oxide film,the blunt current of the base material is much smaller than that of the weld nugget area and the heat(thermo mechanically)influence zone,and it is easier to passivate;when the thickness of the micro-arc oxide film is 50μm,the base material is blunt The current is less than the weld nugget zone and the heat(thermo mechanically)influence zone.The thinner micro-arc oxide film has no obvious effect on the improvement of joint corrosion inhomogeneity;when the thickness of the micro-arc oxide film is 70μm,the passivation characteristics of different regions of the joint are closing,the micro-arc oxide film helps to reduce the influence on the unevenness corrosion of joint structure in different areas of the joint.