Intergranular corrosion of spark plasma sintering assembled bimodal grain sized AA7075 aluminum alloys

The bimodal grain sized 7075 aluminum alloys with different mass fraction of coarse and fine grains were sintered by spark plasma sintering (SPS). The effects of grain size on intergranular corrosion (IGC) were estimated by immersion tests, electrochemical measurements and complementary techniques including SEM-EDS and TEM-EDS. The results showed that the IGC depth decreased significantly with the increasing ratio of fine grains, demonstrating a less IGC susceptibility in the fine grains. The bigger size, more continuous feature and higher iron and copper content of intermetallic particles in coarse grains resulted in faster cathodic reaction rate and consequently higher IGC susceptibility.