Spheroidization of the Al-Si Eutectic in a Cast Aluminum Alloy

Samples from a cast aluminum alloy were heat treated at 470 °C for periods of times ranging from 2 to 40 h to study the spheroidization of the silicon particles of the Al-Si eutectic aggregate. The specimens were obtained from small ingots cast in metallic and sand molds with different amounts of strontium added to modify the aspect ratio of the silicon platelets. It was found that these particles have the tendency to change their shape from elongated to round as time elapses at the heat treating temperature, although small changes in length and width were observed at times shorter than 10 h. It was found that the interparticle separation distance increased with time; this effect was more pronounced in samples that contained the higher amounts of strontium and were cast in metallic molds.