On the development of a pseudo micro-truss intermetallic microstructure in a high pressure die cast AZ91 alloy

The three dimensional features of the intermetallic microstructure that develop across the thickness of a 1 mm thick casting has been studied using SEM and dual beam FIB. The intermetallics form a closely interconnected spatial network which resembles a scaffold or micro-truss structure near the casting surface. The degree of interconnection decreases, and the overall scale of the microstructure is coarser at the core of the casting. The contribution of this pseudo micro-truss structure to the overall strength of the casting is discussed.