Research Article
Formation Mechanism of Primary Si Free Zone in Unidirectional Solidified Al-17%Si Alloy Casting
2015 Volume 87 Issue 2 Pages 117-123
Details
2015 Volume 87 Issue 2 Pages 117-123
Hyper eutectic Al-Si alloys are used for making pistons and cylinder blocks due to their good wear resistance. However, the primary silicon free zone (PSFZ) is formed at rapidly cooled areas. Thus in this study, attempts were made to clarify the formation mechanism of PSFZ. Solidification was carried out using Al-17%Si alloy without phosphorus, and the following results were obtained.
The primary silicon phase was nucleated on the chiller. All other areas were PSFZ. This finding suggested that coupled growth occurs in the PSFZ area because the primary silicon phase cannot grow. The reason for this could be explained by considering the relationship between the growth velocity of primary silicon and aluminum atom transfer rate.
