Effect of sc and zr additions on recrystallization behavior and intergranular corrosion resistance of al-zn-mg-cu alloys

Abstract

The recrystallization and intergranular corrosion behaviors impacted by the additions of Sc and Zr in Al-Zn-Mg-Cu alloys are investigated. The stronger effect of coherent Al3 (Sc1−xZrx) phases on pinning dislocation resulted in a lower degree of recrystallization in Al-Zn-Mg-Cu-Sc-Zr alloy, while the subgrain boundaries can escape from the pinning of Al3Zr phases and merge with each other, bringing about a higher degree of recrystallization in Al-Zn-Mg-Cu-Zr alloy. A low degree of recrystallization promotes the precipitation of grain boundary precipitates (GBPs) with a discontinuous distribution, contributing to the high corrosion resistance of Al-Zn-Mg-Cu-Sc-Zr alloy in the central layer. The primary Al3 (Sc1−xZrx) phase promotes recrystallization due to particle-stimulated nucleation (PSN), and acts as the cathode to stimulate an accelerated electrochemical process between the primary Al3 (Sc1−xZrx) particles and GBPs, resulting in a sharp decrease of the corrosion resistance in the surface layer of Al-Zn-Mg-Cu-Sc-Zr alloy.