The effect of sensitization on the corrosion susceptibility and tensile properties of AA5083 aluminum

Aluminum-magnesium alloy (AA5083-H116) is primarily designed for marine applications such as in ship hulls and deckhouses. Its excellent combination of physical and mechanical properties makes it useful for other applications such as aircraft construction, military equipment and vehicles and automobiles.This study investigated the effect of time and temperature of sensitization on the mechanical and chemical properties of AA5083-H116 such as tensile strength, yield strength and susceptibility to intergranular corrosion (IGC). Test specimens were sensitized at various temperatures (80oC, 100oC, 175oC and 200oC) for up to 672 h (4 weeks). Microhardness measurements, tensile testing, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), inductively coupled plasma/mass spectrometry (ICP/MS) and nitric acid mass loss tests (NAMLT) were used to evaluate these effects. The results obtained show that the mechanical properties of AA5083-H116 deteriorated with increasing sensitization temperature and time. The adverse effect on these properties was attributed to reduction in dislocation density and recrystallization at higher temperatures. The as-received specimens and those sensitized at 80oC showed no susceptibility to IGC. However, at higher sensitization temperatures and longer resident times, resistance to IGC decreased dramatically. The reduction in IGC resistance was attributed to precipitation of secondary phases along the grain boundaries