Effect of grain size and second phase on the corrosion behavior of MIG-welded Al-Mg-Si-Mn-Cr alloy

The effect of grain size and second-phase distribution on the corrosion performance of metal inert gas-welded Al-MgSi-Mn-Cr alloy in different regions was investigated. Due to the welding heat, the transformation of the strengthening phase beta '' (Mg5Si6) to B ' phase (Al3Mg9Si7) in heat-affected zone I leads to the reduction in strengthening ability of the joint. In comparison with the equiaxed grain of weld zone, base metal exhibits high grain boundary density of the fibrous grain and a large amount of second phases on the grain boundary, which increases the anodic dissolution site, leading to the highest pitting corrosion susceptibility. Additionally, the continuous distribution of beta (Mg2Si) precipitate and Al(MnFe)Si dispersoid at grain boundary forms a corrosion channel, which promotes the corrosion propagation along grain boundary. [GRAPHICS] .

Automated summary

The effect of grain size and second-phase distribution on the corrosion performance of Al-MgSi-Mn-Cr alloy was investigated. The transformation of the strengthening phase in the heat-affected zone reduced the joint's strengthening ability. The high grain boundary density and presence of second phases in the base metal increased the pitting corrosion susceptibility.