摘要
The nucleation of eutectic crystals of hypoeutectic A1-7 wt pct Si-Mg casting alloys modified by Ce and Sr was studied by using differential scanning calorimeter （DSC） and scanning electron microscope （SEM）. DSC results were applied to calculate the values of activity energy and nucleation work of eutectic nucleation for the alloys. These values were decreased and the eutectic nucleation frequency was increased with the addition of Ce and Sr to the alloys. Moreover, the morphology of eutectic silicon in the modified alloys was partially or fully modified as fine, fibrous or coral, and DSC plots show that the eutectic undercooling of A1-7 wt pct Si-Mg alloys were increased with additions of modified agents. The mechanism of eutectic modification is combined actions of the accelerated nucleation and the restricted growth.
The nucleation of eutectic crystals of hypoeutectic A1-7 wt pct Si-Mg casting alloys modified by Ce and Sr was studied by using differential scanning calorimeter （DSC） and scanning electron microscope （SEM）. DSC results were applied to calculate the values of activity energy and nucleation work of eutectic nucleation for the alloys. These values were decreased and the eutectic nucleation frequency was increased with the addition of Ce and Sr to the alloys. Moreover, the morphology of eutectic silicon in the modified alloys was partially or fully modified as fine, fibrous or coral, and DSC plots show that the eutectic undercooling of A1-7 wt pct Si-Mg alloys were increased with additions of modified agents. The mechanism of eutectic modification is combined actions of the accelerated nucleation and the restricted growth.
基金
financially supported by Research Fund of the State Key Laboratory of Solidification Processing (No. 42-QP-009)
the 111 Project of China (No. B08040)
