Reduction in secondary dendrite arm spacing in cast aluminium alloy A356 by Sb addition

The effects of Sb on the secondary dendrite arm spacing (SDAS) were investigated in directional solidification experiments under different cooling rates. The addition of Sb reduced the average SDAS at higher Sb contents. The most effective reduction occurs at 0.12 wt-%Sb. Our results also reveal a reduced variation in the SDAS upon the addition of Sb in the higher range, i.e. 0.18-0.30 wt-%. We suggest that the reduced variation in the SDAS upon addition of Sb in this range resulted from the interaction between the accumulation of Sb at the solid/liquid interface that increases the instability at the solid/liquid interface and later decreases the SDAS and a high concentration of Sb that increases the accumulation of Sb at the solid/liquid interface and results in a larger amount of AlSb or Mg3Sb2 intermetallic phases and a higher latent heat.