Precipitation behavior of the ß phase in Al-5083

The formation and growth of the magnesium-rich ß phase, Al3Mg2, in Al-5083 has been studied by transmission electron microscopy (TEM). The ß phase forms heterogeneously both at grain boundaries, and on preexisting particles which are enriched in manganese. The ß precipitates at grain boundaries, containing a high density of very fine faults, thicken faster than the rate estimated assuming volume diffusion controlled growth of planar interfaces. It is suggested that pipe diffusion through dislocations contributes to the enhanced growth rate.