EFFECT OF ALLOYING ELEMENTS ON PARTICULATE DISPERSION IN LIQUID ALUMINUM

The effect of alloying elements on dispersion of SiC particles into molten aluminum was investigated. The time required for incorporation is defined as incorporation time. The incorporation time of SiC was shortened by alloying magnesium or by alloying titanium together with tin. These alloying elements have a strong affinity for SiC and are able to form silicide as a result of reaction with SiC. Magnesium silicide was detected by EPMA, although the existence of titanium silicide could not be confirmed. The incorporation time was prolonged by adding zinc, copper or tin which has no affinity for SiC. Particulate dispersion is considerably influenced by surface active elements with strong affinity for SiC, whereas it was prolonged by adding the surface active elements such as lead or bismuth having weak affinity for SiC. This is probably because lead or bismuth hinders the wetting between SiC particle and molten aluminum, adsorbing at the interface. The addition of silicon prolonged the incorporation time of SiC because dissociation of SiC that might be necessary for good wetting was controlled by the silicon.