An investigation on primary Si refinement by Sr and Sb additions in a hypereutectic Al-Si alloy

The effect of Sr and Sb additions as potential primary Si refiners for A390 hypereutectic Al alloy was analyzed. Despite the impurity induced twining (IIT), the experimental results indicate that only twin formation is not responsible for primary Si refinement. Stacking fault, by enforcing the atoms to adjust the sequence, and kinks, by deviating the Si growth from its easy growth direction, cooperate in growth discontinuity. An enhanced IIT theory has been proposed for primary Si evolution where twining, stacking faults and kinks are contributing to control the Si growth. Type of alloying element determines the major contributing mechanism in primary Si evolution. To the best of Authors’ knowledge, the kink formation and its effect on primary Si refinement has yet been reported elsewhere.