Transformation of microstructure after modification of A390 alloy
(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Zhengzhou Research Institute of China Aluminum Company, Zhengzhou 450041, China)
2. Zhengzhou Research Institute of China Aluminum Company, Zhengzhou 450041, China)
Abstract: A hypereutectic aluminum-silicon alloy with content of 17%Si, designed as A390, was modified. The change of microstructure was identified by optical microscopy. The results show that phosphorus can change the morphology and size of the primary silicon and control the length of needle-like eutectic silicon or dendrite. After modified by phosphorus, the primary silicon of star-like and coarse platelet is changed to polygonal with less cute angles and decreasing average size. The eutectic silicon is also changed because it grows from the tip of angles on the primary silicon and is influenced by the morphology and size of primary silicon. The eutectic silicon changes from needle-like or dendrite shape to short bars and dots with less average length.
Key words: aluminum-silicon alloys; modification; phosphorus; primary silicon; eutectic silicon