Evolution of iron-rich intermetallics and elevated temperature mechanical properties in gravity die cast 2A16 Al alloy

The evolution of iron-rich intermetallics and the mechanical properties at elevated temperature in gravity die cast 2A16 alloys with a high Fe content of 0.5 wt-% were investigated using SEM, TEM, deep etching technique, and tensile test. The results showed that the Chinese script-like alpha-Fe transforms to the beta-Fe phase during T7 heat treatment. The newly formed beta-Fe with a cylindrical shape minimised their surface area. A nano sized alpha-Fe dispersoid was found in the a (Al) matrix in Al-Cu alloys with high Fe content during T7 heat treatment. At the elevated temperature of 573 K, the 2A16 alloys with high Fe content of 0.5 wt-% showed superior tensile properties compared to those of the commercial aluminum alloys, and this is attributed to the prevention of grain boundary sliding resulting from the presence of beta-Fe and the long term thermal stability of nanosized alpha-Fe dispersoids in the alpha (Al) matrix.