Fading of Sodium in AlSi7Cu0.5Mg Alloy Studied Using Thermal Analysis Technique

The modification of silicon particles in as-cast aluminum alloys can be done with different modifiers. Sodium is the strongest one not so often used in aluminum casting plants. This is because sodium fading is considerably vigorous compared to other modifiers. This study examined the effect of sodium fading on the modification level of silicon particles in the AlSi7Cu0.5Mg (356) aluminum alloy. The cooling curve analysis has been applied to quantify sodium fading. Approximately 65 ppm of sodium in the tablet form was added to the melt. The sodium was held for 200 minutes in the melt to observe its fading. It was found that sodium does not fade rapidly, as the literature data proposed. Furthermore, it was recognized that modification with sodium produces more dross that can have a negative impact on the quality of cast parts if it is not properly removed from the melt. Besides thermal and chemical analysis, an image analysis technique can be additionally used as a quality control tool to assess the efficiency of modifiers.