Enhanced castability of multi-element hypoeutectic Al-Si alloys via synergistic microalloying with Sb and La

Abstract

Fluidity and volume shrinkage are important factors that define the castability of aluminum casting alloys, which is the prerequisite for production in industry. Due to the casting of the alloy being a complex solidification process, it is hardly enough to explain the castability by a single experiment or theory. In this paper, the effects of Sb and La on the castability of multi-element hypoeutectic Al-Si alloy are revealed by combining thermodynamic calculation, finite element simulation, and experiment. The results show that the rheological mechanism indicated the morphology and size of eutectic silicon will affect the fluidity. Meanwhile, the addition of Sb and La would reduce the viscosity and increase the enthalpy of the alloy, thus enhancing its fluidity. Based on this, a new mathematical model for predicting the spiral length is put forward. The viscosity and enthalpy of the alloy introduce a new mathematical model, which conforms to the rheological mechanism. Additionally, the addition of Sb can reduce the shrinkage porosity of the alloy, and the addition of Sb and La enhances the fluidity of the alloy, which improves the feeding effect of the alloy in the paste zone at the end of solidification and reduces the volume shrinkage of the alloy. When Sb and La are added to the alloy, the liquid contraction of the alloy is reduced from 0.033 %/°C to 0.028 %/°C at the same pouring temperature for the alloy with Sb and La addition.