In order to clarify the influence of mold temperature, phosphorus, and calcium on the characteristics of ADC12 alloy, investigations were carried out using a Tatur mold and thermal analysis. Phosphorus increases the number of eutectic nucleation sites by forming AlP, slowing down the timing at which the solidification shell is formed. Due to this reason, exterior shrinkage is suppressed compared to interior shrinkage. Calcium changes the formerly produced AlP into Ca₃P₂, reducing the number of eutectic nucleation sites. This as a result slows down the timing at which the solidification shell is formed. Therefore, in contrast to phosphorus, exterior shrinkage increases and interior shrinkage decreases. These changes can be observed in the eutectic temperatures. In addition, since the increase in the temperature of the mold delays the formation of the solidification shell, the exterior shrinkage increases and the interior shrinkage decreases. In this condition, porosity increases.

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  It is well known that controlling the graphite shape in cast iron is a critical issue to achieve appropriate properties. It is of interest to know how the microstructure in cast iron evolves during solidification. So far, time-evolution of the microstructure has not been observed in-situ. This paper presents the in-situ observation results of cast iron solidification using X-ray imaging of synchrotron radiation. Transmission X-ray images with a spatial resolution of as small as 5μm were obtained by an X-ray detector SATICON in an imaging beam line 20B2 at SPring-8. A 10 × 10 × 0.1mm specimen was melted and solidified in a mold made of Al₂O₃ placed in a vacuum chamber. The observation showed that the solidification started with austenite dendrites, after which the eutectic structure was formed. Graphite clusters of about 100μm in diameter were formed in the remaining liquid surrounded by the eutectic structure at a cooling rate of less than 10K/min. At a cooling rate of 10K/min, the primary dendrite and the eutectic grains moved up and down, respectively, due to the bouncy force.

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