Solidification characteristics and mechanical properties of hypoeutectic aluminum-silicon alloy containing sulfur

Abstract

The present study reports experimental findings concerning the effect of sulfur on A356 alloy. Although it is found that sulfur can affect eutectic reaction of aluminum-silicon alloys, limited work pertaining thereto is published and no detailed study is available. It is of metallurgical interest to have a better understanding regarding the influence of sulfur on solidification as well as mechanical properties of the alloy. In this study casting experiments were conducted on a hypoeutectic grade aluminum-silicon alloy, A356, with sulfur addition. Thermal analysis shows that the eutectic reaction temperature of the A356 alloy containing sulfur is higher than that of the normal alloy and that the time interval of the eutectic reaction of the sulfurized alloy is longer. Series of microscopic examination of as-cast samples suggest some interesting findings. In contrast to the normal case, eutectic silicon phase of the alloy containing sulfur tends to appear in form of cluster comprising of broken acicular-like silicon phase. Although there seems to be no differences in ultimate tensile strength as well as bulk hardness between the sulfurized alloy and the normal A356, it is evident that yield strength and ductility of the A356 alloy are reasonably altered with the presence of sulfur. The A356 alloy containing sulfur exhibits greater ductility and lower yield strength in comparison with the normal A356 alloy.