Effect of trace elements on the microstructure and porosity formation in 319 type aluminum-silicon-copper alloys

Since Sr-modified alloys are invariably employed in the production of automotive castings, it is important to have knowledge of the effect of such impurities on the Sr-modification process in terms of any interactions between them, and the consequent effect on the final product.; With the increased use of secondary materials in production, and in view of the fact that information in this area is scarce, this aspect becomes important enough to require a detailed study. The present work was therefore undertaken to quantify the effects of Sr-Bi and Sr-Ca interactions and their impact on the eutectic silicon particles characteristics (which would provide a measure of the effectiveness of the modification treatment) in Sr-modified 319 alloys containing 0.04 and 0.4wt% Mg. As Sr modification is almost always associated with an increase in the porosity level of the alloy, and since the presence of porosity is known to be detrimental to the alloy properties and casting quality, the effect on porosity formation was also studied. (Abstract shortened by UMI.)...