Filiform corrosion behaviour on machined AA7150 aluminium alloy

机加工AA7150铝合金的抗丝状腐蚀性能

The microstructure and the filiform corrosion behaviour of machined AA7150 aluminium alloy were investigated using scanning and transmission electron microscopies combined with potentiodynamic polarization and filiform corrosion testing,respectively.It is found that the grain refinement,redistribution of alloying elements,and elements segregation at grain boundaries are evident within the near-surface region on the machined AA7150 aluminium alloy.The corrosion susceptibility of machining introduced near-surface deformed layer is significantly improved caused by the modified microstructure associated with severe deformation.Filiform corrosion resistance on the machined surface is obviously decreased,due to the surface roughness associated with machining tracks and the presence of the electrochemically more active near-surface deformed layer introduced by machining.

采用扫描及透射电子显微技术表征机加工AA7150铝合金近表面变形层的显微组织,并结合动电位极化曲线及丝状腐蚀测试研究机加工后AA7150铝合金的丝状腐蚀行为。研究发现,机加工后AA7150铝合金近表面区域出现晶粒细化、合金元素重新分布以及晶界偏析等特征。机加工过程中强烈的塑性变形导致近表面区域显微组织的改变,从而极大地提高合金近表面变形层的腐蚀倾向。机加工使合金表面粗糙度增大,并导致形成电化学活性明显提高的近表面变形层。在二者共同影响下,机加工后AA7150铝合金的抗丝状腐蚀性能明显下降。