Fatigue crack propagation behaviour and corrosion resistance of Al–Zn–Mg–Cu–Ti(–Sn) alloys

Abstract

The propagation of a fatigue crack in and the intergranular corrosion (IGC) behaviour of Al–Zn–Mg–Cu alloys with and without the addition of Sn were tested, and the microstructures of these alloys were further analysed using optical microscopy, scanning electron microscopy and transmission electron microscopy. It was found that the addition of Sn refines the solution aging grain size and reduces the width of the precipitation free zones, which results in reinforcement of the alloy's fatigue crack propagation resistance. In addition, discontinuous distribution of grain boundary precipitates in the Sn containing alloy directly leads to a higher IGC resistance.