Influence of annealing temperature on sensitisation behaviour and corrosion properties of an Al-6.8wt% Mg alloy

Abstract

Influence of annealing temperature on beta-(Al3Mg2) phase precipitation and corrosion properties of sensitised Al-6.8wt% Mg alloy is investigated. Sensitisation of specimens annealed at 320 degrees C results in IGC and SCC susceptibility. Microstructural characterization shows fine precipitation of Mg-rich phase forming nearly continuous film at grain boundaries, despite small precipitated fraction (0.5%), and grain boundary faceting. Sensitised specimens annealed at 265 degrees C are IGC susceptible, but SCC resistant. Precipitation at grain boundaries is discrete, although the precipitated fraction is greater (3%) than in specimens annealed at 320 degrees C. Potentiodynamic measurements show that of all measured parameters, charge density is in the strongest correlation with the NAMLT and SSRT results.