Influence of DC and AC Magnetic Fields on the Solidification Structures of Al-Fe-Si Alloys

The effects of the DC and AC magnetic fields on the phase composition, morphology and distribution of the ternary Al-Fe-Si alloy were investigated. The solidification structures of the alloy solidified with and without the application of magnetic fields were confirmed by DSC and structural measurements. The results showed that, Fe/Si ratio plays an important role in determining the reaction type, which in turn affects the phase composition, morphology. As for the alloy with the Fe/Si ratio 1.2, the elongated needle-like Al(3)Fe phase was the dominant phase in the dendritic regions with the minor amount of Chinese script-like alpha-AlFeSi. As for the alloy with the Fe/Si ratio 0.2, the Chinese script-like alpha-AlFeSi was the dominant phase, accompanied with a small amount of needle-like beta-AlFeSi and granular Si. In these Al-Fe-Si alloys, the homogeneous distribution of the intermetallics formed in the interdendritic regions was achieved with the application of the DC magnetic field. However, the intermetallic phases were accumulated towards the sample center with the application of the AC magnetic field. This was attributed to the accumulation of the iron-containing cluster and silicon-containing cluster at the melt center. Furthermore, the amount of Chinese script-like alpha-AlFeSi was increased remarkably in the former alloy under AC magnetic field, while in the latter alloy, the amount of beta-AlFeSi and Si was increased under AC magnetic field.