Effect of iron addition on graded microstructure of Al-13.8 wt.% Mg2Si during centrifugal casting

The modification of microstructural grading of the cast hollow cylinders of eutectic composite Al-13.8 wt.% Mg2Si was studied via 0.5 wt.% Al-75Fe addition to the melt during centrifugal casting. The chemical composition, microstructure and hardness of different radial sections of the cast cylinders were studied using energy dispersive spectroscopy (EDX), optical microscope, scanning electron microscope, X-ray diffractometry and hardness testing, respectively. The results show that due to specific thermal regime, prevailed in centrifugal casting, the rod-shape fine eutectic microstructure in external periphery of the cast hollow cylinder changes to a coarse lamellar-shape eutectic microstructure in its internal periphery of cylinder. Also owing to segregation of FeAl3/Al8Fe2Si brittle particles with needle morphology towards the inner periphery of cylinder, thus their effective role in heterogeneous formation of Mg2Si and developing the α-Al in matrix phase, the inner periphery of the iron-contained cylinder showed the lower hardness in compared with the outer periphery of cylinder.