The microstructure of a Mg-10 wt.%Al alloy

A structural analysis of a nonstandard Mg-10 wt.% Al alloy has been performed. Structural examinations were carried out for the alloy either in the as-cast state and after T6 heat treatment involving solutioning and artificial ageing. In the cast alloy, the presence of the degenerated eutectic (Mg) + gamma was disclosed, which occurred as a result of a strong segregation during solidification. The T6 heat treatment resulted in a homogenization of the solid solution and the formation of a large number of secondary gamma' precipitates with a characteristic lamellar morphology. Transmission electron microscopy allowed the determination of two crystallographic orientation relationships between the gamma' and the (Mg) phases: (0001)(Mg) parallel to (1 (1) over bar0)gamma', [2 (1) over bar(1) over bar0](Mg) parallel to [111]gamma' and (0001)(Mg) parallel to (1 (1) over bar0)gamma', [0 (1) over bar 10](Mg) parallel to [113]gamma'.