Decomposition of solid solution of the AA5083 alloy upon exposure to elevated temperatures

The soft temper plates of the AA5083 alloy are widely used in the transportation industry, for example in the construction of land transportation vehicles such as tanker lorries. Currently the use of this alloy is limited to those applications where the service temperature is less than 65°C. This limitation originates from an anticipated susceptibility of this alloy to intergranular and stress corrosions during service at temperatures above 65°C. The susceptibilities to intergranular, and hence stress corrosions, in turn, originates from the precipitation of Mg containing anodic intermetallics on the grain boundaries. Understanding the decomposition of Mg in solid solution is therefore of paramount importance to finding solutions that might widen the scope of high Mg containing 5xxx alloys and is the theme discussed in the paper. This paper discusses the decomposition behaviour as determined using the conductivity, weight loss and thermoelectric potential measurements.