Study On Corrosion Behavior And Mechanism Of Al-Cu-Mg-Ag New Heat Resistant Aluminum Alloy

Al-Cu-Mg-Ag alloy is a new kind of heat resistance Al alloy based on the 2 series heat-resistance alloy.It possesses excellent performance at elevated temperatures and has wide application prospect in the aerospace field.However,2 series aluminum alloys have high corrosion sensitivity,and corrosion is one of the important failure forms of material failure which has an important influence on its application in practical engineering.In this paper,Al-Cu-Mg-Ag alloy was prepared by ingot metallurgy method.Intergranylar corrosion,exfoliation corrosion,electrochemical analysis,metallographical observation and transmission electron microscopy analysis were carried out to investigate the effects of alloying elements,rolling and heat treatment possess on the corrosion resistance and microstructure of the alloy.The results are as follows:With the increase of Mg content,the hardening process of the alloy is accelerated,the recrystallized grain size increases;the number of the phases of Al-Cu-Mg-Ag alloy at the grain boundaries and inside the grain increases;the potential difference between PFZ and the matrix increases gradually,and correspondingly,the intergranular corrosion rate of the alloy decreases;for the two factors,the potential difference between PFZ and the matrix and the wedging force caused by grain boundary corrosion products decreases,resulted in the exfoliation corrosion resistance of the alloy decreases first and then increases.With the increase of Ag content,the hardening process of alloy is sped up;precipitations change from a large number of ?' phase and a small amount of ? phase into many ? phase and a small amount of ?' phase;PFZ width decreases,the corrosion channel become narrow,and correspondingly,the intergranular corrosion resistance and exfoliation corrosion resistance are both enhanced.The increase of cold deformation can improve the peak aging hardness of Al-Cu-Mg-Ag alloy,what's more,it can make recrystallization grain refined and the width of PFZ decreased;on the effect of the two factors of narrowing PFZ and refined grain,the intergranular corrosion resistance of the alloy increases and the exfoliation corrosion resistance decreases first and then increases with the increase of cold deformation.The sample with a 50% cold deformation possesses the best exfoliation corrosion resistance.With the extension of solution time,the number of precipitations on the grain boundaries and inside the grains increases,which makes the potential of PFZ on grainboundary decreased,therefore,the corrosion rate of the alloy are accelerated.With the increase of pre-tension deformation,the process of heterogeneous nucleation of ? phase and ?' phase are accelerated,and the precipitations inside the grain and on the grain boundaries are refined.Besides,the precipitation of ? phases is suppressed and the precipitation of ?' phase is accelerated.The width of PFZ decreases,which enhances the intergranular corrosion resistance of the alloy.The increase of corrosion products which caused by elongated grain in unit volume makes the wedging force increased,therefore,the exfoliation corrosion resistance decreases.