The effect of strontium on the microstructure of the aluminium-silicon andaluminium-copper eutectics in the 319 aluminium alloy

The influence of strontium on the silicon modification and aluminium-copper eutectic microstructures in the 319 aluminium alloy was examined. The stro ntium levels considered were between 8 and 96 ppm. The purpose of this study is: (i) to observe the effects of strontium on th e degree of silicon modification in the 319 aluminium alloy, and (ii) to de termine the effects of strontium level on the area fraction of copper phase s. The degree of silicon modification was determined using the American Foundr ymen's Society (AFS) specification. The area fractions of aluminium-copper phases were examined using scanning electron microscopy (SEM) and quantitat ive image analysis (IA). This investigation showed that a strontium level between 75 and 85 ppm was sufficient to modify the thermal analysis test sample's silicon structure t o an AFS specification No. 4. Increasing the strontium level from 8 to 96 p pm leads to the larger area fraction of the interdendritic blocky Al2Cu eut ectic structure and lower area fraction of the eutectic Al-Al2Cu structure with interspersed alpha-Al phase in the as-cast structure.