Effect of sensitization heat treatment on properties of Al–Mg alloy AA5083-H116

Al–Mg alloy AA5083 is a sheet and plate alloy used mainly for marine application as well as for structural components in transportation and military applications. The strength is derived from solid solution strengthening and strain hardening. The properties of as-received and sensitized samples of AA5083-H116 were investigated using microhardness measurements, tensile testing, optical microscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and Nitric Acid Mass Loss Test (NAMLT). The results show that both chemical and mechanical properties of the alloy decreased with increasing sensitization temperature and time. The deterioration in chemical property, which was measured in terms of the level of susceptibility to Intergranular Corrosion (IGC), is attributed to grain boundary precipitation of magnesium-rich particles. The loss in tensile and hardness properties is attributed to softening caused partly by decrease in Mg solute solid solution concentration with increasing sensitization time and temperature and partly by recrystallization at elevated temperatures.