The microstructures of aluminum-base alloys are more complex than those of low-alloy steels, for example, because of the variety of intermetallic particles present in the microstructure. That this is the case is illustrated by the optical micrographs in Figures 1 through 3. The intermetallic particles usually present in the microstructure of 2024 Al are Al(Mn,Fe), Al7Cu2Fe and Al2CuMg.
Figures 4 through 9 are SEM micrographs of the same microstructure. An interesting feature of the micrographs in Figures 7 and 9 is the triangular-shaped etch pits produced by the chemical attack on the fcc matrix of the alloy.