Precipitation crystallography of plate-shaped Al6(Mn,Fe) dispersoids in AA5182 alloy

The habit plane, orientation relationship (OR) and interfacial structure between the plate-shaped Al6(Mn,Fe) dispersoids and Al matrix in an AA 5182 alloy have been systematically studied by transmission electron microscopy, selected-area electron diffraction and crystallographic simulation. The published OR data about the dispersoids precipitated in different Al alloys has been critically assessed. A precise OR has been determined as (0 0 1)p//(3 −1 5)m and [−1 1 0]p//[2 1 −1]m, while the habit planes are determined as (0 0 1)p and (3 −1 5)m. The OR and habit plane have been discussed in terms of the Δg approach. The dislocation arrangements at the interphase boundary of the habit planes are calculated by using O-lattice theory, which has been used to explain the mechanism of the OR selection and morphology development of dispersoids. It is revealed that an atom-to-atom matching exists in the good matching regions between the dislocations in the habit plane.