Corrosion Behaviors Of Friction Stir Welded Joint Of 7050 Aluminum Alloy

The develop of Friction stir welding(FSW)has greatly promoted the fabrication of complicated components from aluminum alloy,as the hot cracking sensitivity that exposes in conventional welding was eluded.Although FSW endues aluminum alloys jointed better retention of baseline mechanical properties and fewer weld defects,this process still produces modified microstructures which influences mechanical properties as well as corrosion resistance.For instance,welded components uffer from more serious corrosion to compare with the non-welded structures,which then restrict the applications that exposed to corrosive evironment.It is thus of significance to investigate what corrosion resistance changes may generate after FSW.This paper investigates the relationship between microstructure and corrosion behavior of 7050-T76 aluminum FSW firstly,and then discusses the impact of welding parameter and base material treatment state on corrosion behavior,and finally explore the feasibility whether the postweld heat treatment can improve the corrosion resistance of FSW joint.The corrosion behavior of various regions of 7050-T7651 aluminum alloy friction stir welding joint and their interaction was studied,and the influence of the microstructure and component difference on corrosion behavior was analyzed.The 3D corrosion potential of FSW welded joint was obtained by electrode beam technology.Results indicate that the HAZ and the bottom of NZ is the most sensitive to corrosion,preferentially corroded as anode.The macro-galvanic corrosion effect between different zones was more remarkable than micro-galvanic corrosion between Al7Cu2 Fe and matrix in this research based on in-situ observation.The variation of rotational speed has no significant effects on microstructure and corrosion behavior.The treatment condition of base material has a remarkable influence on corrosion behavior.The potential difference of FSW weled joint which base material is in solution condition(SSW)is smaller,leading the weaker macro-galvanic corrosion effect between different zones and more homogeneneous corrosion,compared with FSW weled joint which base material is in T76 condition(T76W).Postweld heat treatment can significantly improve corrosion behavior of FSW welded joint.The potential difference of the joint abtained by carrying T76 treatment on SSW is smaller than T76 W,resulting in weaker macro-galvanic corrosion effect between different zones.