The response of microstructure in high strength Al-Zn-Mg-Cu aluminum alloy 7055 to Graff Sargent etchant was investigated. It was found that grain boundaries and subgrain boundaries were easily corroded due to presence of η phase, and grain boundaries were corroded more rapidly than subgrain boundaries. The grain structure could be revealed quite clearly after immersion for about 15s. S (Al2CuMg) and Al7Cu2Fe phase were quite stable during immersion if the time was not very long. A dealloying for Al/Mg in the S and Al7Cu2Fe phase was found after long time immersion. Prolonged immersion resulted in serious corrosion of subgrain boundaries, consequently separation of fine subgrains.

Crystal structure and X-ray powder diffraction data for the Al7Cu5Y ternary compound are presented. The compound crystallizes in the body-centered tetragonal with the Al7Fe5Y structure type (space group I4/mmm), the lattice parameters a = 8.6960(9) Å, c = 5.1256(7) Å, V =387.62 Å3, Z =2, ڑx =5.102 g/cm3, F30 = 275.5(0.0033, 33) and RIR =1.23.