Spheroidization of the Al-Si eutectic in a cast aluminum alloy

Samples from a cast aluminum alloy were heat treated at 470 degreesC for pe riods of times ranging from 2 to 40 h to study the spheroidization of the s ilicon particles of the AI-Si eutectic aggregate. The specimens were obtain ed 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 fro m elongated to round as time elapses at the heat treating temperature, alth ough small changes in length and width were observed at times shorter than 10 h. It was found that the interparticle separation distance increased wit h time; this effect was more pronounced in samples that contained the highe r amounts of strontium and were cast in metallic molds.