Scanning electron microscopy has been used to characterize the intermetallic structure development across the tensile cross-section of binary Mg-Al alloys with solute content between ~0.5 and 12 mass%Al. The alloys which contain less than 1 mass%Al exhibited a single phase grain structure. For compositions greater than 1 mass% Al, an eutectic network with a discontinuous distribution of intermetallics across the cross-section became apparent. In alloys with greater than 8.77 mass%Al, the intermetallics form a continuous network over the entire cross-section. The scale of the intermetallics network is finer at the surface and corner regions of the cross section in comparison with the core regions.