Effects of electromagnetic stirring and rare earth compounds on the microstructure and mechanical properties of hypereutectic Al–Si alloys

In this paper, the effects of rare earth addition and electromagnetic stirring on the microstructure and the mechanical properties of hypereutectic Al–Si alloys have been reported. Hypereutectic Al–Si alloy was prepared using liquid metallurgy route and modified with the addition of cerium oxide. To control the structure, slurry of hypereutectic Al–Si alloy was subjected to electromagnetic stirring before pouring into the mould. It was observed that the addition of cerium oxide (0.2 wt.%) refined the primary silicon particles and modified the eutectic silicon particles. Further, the electromagnetic stirring of the hypereutectic Al–Si alloy reduced the average size of primary silicon particles, from 152 ± 9 to 120 ± 6 μm, and the length of β-intermetallic compounds decreased from 314 ± 12 to 234 ± 10 μm. Similarly, the application of electromagnetic stirring on cerium oxide-modified hypereutectic Al–Si alloy also reduced the average size of primary silicon particles from 98 ± 5 to 76 ± 4 μm and the average length of β-intermetallic compounds from 225 ± 7 to 203 ± 5 μm. Mechanical properties namely tensile strength, ductility and hardness of the alloys were improved with electromagnetic stirring and addition of cerium oxide appreciably.