Microstructural Evolution and Stress Corrosion Cracking Behavior of Al-5083

The fine scale microstructure of Al-5083 (H-131) sensitized at 448 K (175 °C) for 1, 10, 25, 50, 100, 240, 500, and 1000 hours has been investigated using transmission electron microscopy (TEM) to study the evolution of the β phase (Al₃Mg₂) at grain boundaries and on pre-existing intragranular particles. In fully sensitized Al-5083, the β phase (Al₃Mg₂) forms heterogeneously both at grain boundaries and on pre-existing particles, which are enriched in manganese. TEM observations showed that the grain boundary precipitation of the β phase initially occurs between 0 to 1 hour of aging at 448 K (175 °C), and that the β phase grows with a ribbonlike morphology. The grain boundary planes are covered by the β phase after 240 hours of aging. The contribution of microstructure, defects, and environment on the stress corrosion cracking (SCC) behavior is discussed.