Effect of Different Modifiers on Microstructure and Strength of Locally Developed A356 Al-Si Alloy

Abstract

The present research aims to study the effect of various combination of salt and metal modifiers (SrCl2, KCl and NaCl salts with NaF including Sb & Sr ) on the locally developed A356 Al-Si alloy. A series of different heats with these modifiers were prepared using a pit type furnace. Casting of the molten metal was carried out using sand casting technique and fluxes at various stages followed by degassing. Sr modifier was used as Al-Sr master alloy, while Sb metal was used in high purity form. However salt modifiers were thoroughly dried before plunging at the bottom of the crucible containing the molten metal. It was observed that the samples containing Sr as modifier showed the best results in terms of microstructure & tensile properties as compared to Sb modifier. A combination of SrCl2, KCl with NaF showed almost the similar and well modified microstructure with better tensile properties as compared to the samples containing NaCl with NaF salt modifier.

Effects of antimony on eutectic silicon and fracture mode of A357 alloy at different cooling rates

“…(1) With antimony addition, the eutectic silicon of aluminum-silicon alloys was modified, and the modification effects were related to the cooling rate [10][11][12][13][14]. (2) There are some viewpoints on the mechanism of antimony modifying eutectic silicon.…”

“…Antimony reduced the dissolution rate of silicon in aluminum-silicon alloy melt, limited the crystal growth and modified eutectic silicon [17]. (3) With antimony addition, the mechanical properties of aluminum-silicon alloys increased [10,11]. At present, with antimony addition, the eutectic phases, the fracture mode and the twins of A357 were not studied.…”

“…For example, the modification was because that the existence of antimony reduced the eutectic growth temperature [13]. Antimony reduced the dissolution rate of silicon in aluminum‐silicon alloy melt, limited the crystal growth and modified eutectic silicon [17]. With antimony addition, the mechanical properties of aluminum‐silicon alloys increased [10, 11].…”