EFFECTS OF S AND SB ADDITIONS ON THE MICROSTRUCTURE AND MECHANICAL-PROPERTIES OF THE AL-SI 319-ALLOY

This work shows the effect of simultaneous additions of sulphur and an timony on the microstructure and mechanical properties of the Al-Si 31 9 alloy, containing high levels of iron and manganese. It was found th at sulphur and antimony act independently. The sulphur influences the shape and distribution of the Al-15(Fe,Mn)(3)Si-2 phase, promoting its occurrence as dendritic Chinese script-like morphology. On the other hand, antimony additions help in the formation of a lamellar eutectic structure. As a result of these changes in microstructure, an improvem ent in the values of ultimate tensile strength, elongation to failure and hardness was observed with respect to those shown by the untreated 319 alloy. The concentration ranges of antimony and residual sulphur investigated were 0.10-0.30 and 0.001-0.04 wt %, respectively.