Effect of additives on the microstructure and tensile properties of Al–Si alloys

The present work was undertaken with the aim of studying the microstructural changes as well as variations in the tensile properties of 413.0 alloy. The ultimate tensile strength (UTS), elastic limit (YS) and elongation to fracture (%El) resulting from the addition of alloying elements – strontium (Sr), magnesium (Mg), copper (Cu), silver (Ag), nickel (Ni), zinc (Zn), cerium (Ce) and lanthanum (La) to the base alloy, and heat treatment were measured. Furthermore, the effect of the addition of phosphorus (P) as well as heat treatment on the microstructure and properties of the base alloy 413.0 modified with Sr was studied from the point of view of the interaction between phosphorus and strontium during the solidification process. The findings revealed that the addition of Mg, Cu, Ag, Ni, Zn, and Sr cause an increase in the values of UTS and YS coupled with a decrease in the values of %El of the base alloy 413.0 following the heat treatment. The hardening effect produced by the addition of ∼0.4% Mg is more or less equal to that obtained from the addition of ∼3% Cu. Alloys modified with Sr show high tensile properties. In addition, the results demonstrate that alloys modified with Sr in which P was added possess ductility values of the order of 4–12%, which is much higher compared to the 2% obtained for the non-modified 413.0 base alloy.