The formation of primary Fe-rich intermetallic compound crystals and the effect of TiB 2 and TiC inoculation during solidification of a hypereutectic Al-Fe alloy has been investigated. Both horizontal, near isothermal conditions and vertical, directional thermal gradient conditions were studied using laboratory and synchrotron X-ray radiography. TiB 2 and TiC inoculation enhanced formation of Fe-rich intermetallics under all experimental conditions. Near isothermal solidification resulted in the highest intermetallic number density and average formation rate, whilst increasing the thermal gradient reduced both. A model for intermetallic crystal formation is proposed to explain the effect of thermal gradient and cooling rate on the intermetallic number density and average formation rate.

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A method was developed based on synchrotron X-ray radiography to estimate tip temperatures of 203 Fe-rich intermetallic compound (IMC) particles during directional solidification of Al-Cu-Fe alloys. Tip temperatures showed two distinct IMC populations corresponding to Al 6 (Fe,Cu) and Al 7 Cu 2 Fe, validated by post-solidification microscopy.The IMC tip undercooling of each growing IMC was estimated by comparison with its equilibrium formation temperature. The effect of Fe concentration, cooling rate and grain refiner additions on the IMC tip undercooling was studied. With a large number of IMC particles measured, we show the relationship between solidification parameters, secondary IMC selection and tip undercooling.