Precipitates and corrosion resistance of an Al-Zn-Mg-Cu-Zr plate with different percentage reduction per passes

7055 aluminum alloy plates with the same size were rolled by two processes: small percentage reduction per pass (PRPP) and large percentage reduction per pass, respectively. Meanwhile, the effect of PRPP on the precipitates and corrosion resistance of 7055 aluminum alloy plate was investigated. The mechanisms were analyzed and discussed by optical microscopy (OM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and electron back-scattered diffraction (EBSD) technique. Large PRPP can improve the corrosion resistance. For the plate rolled by small PRPP, the main precipitate is guinier-preston (GP) zone and continuous grain boundary precipitates (GBPs), while, for the plate rolled by large PRPP, the main precipitates are the GP zone and eta' precipitate, and the GBPs are discontinuous.