Evaluation of strontium fading in 319 al alloy using thermal analysis

摘要

The modification of silicon particles in as-cast aluminum alloys can be done with different types of modifiers. Among them, strontium is the most widely used because its fading is considerably slower than that of other modifiers. Strontium influences silicon morphology by changing it from acicular to lamellar or fibrous. This study examined the effect of strontium fading on the size and shape of silicon particles in the 319 aluminum alloy. The measurement of the size of silicon particles formed during solidification was used to quantify strontium fading. Approximately 54 ppm of strontium, in the form of masteralloy (Al-10wt%Sr), was added to the melt and was held for 16 hours. Thermal analysis of the test sample and its image analysis revealed that strontium faded rapidly (in approximately 100 minutes the level of strontium in the melt decreased by 20%). This decrease in the strontium content produced increases in the nucleation temperatures of the copper-rich phases and the solidus temperature.