Effect of ultrasonic melt treatment on structure refinement ofsolidified high purity aluminum
(1. Shanghai Key Laboratory of Advanced High-temperature Materials and Precision Forming,
Shanghai Jiao Tong University, Shanghai 200240, China;
2. State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China)
Shanghai Jiao Tong University, Shanghai 200240, China;
2. State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China)
Abstract: Effect of ultrasonic melt treatment on the macrostructure of solidified high purity aluminum was studied experimentally using metallographic method and complementary numerical calculations of acoustic pressure and velocity distribution in the melt. The results reveal that the macrostructure is effectively refined within a cone-shaped zone ahead of the irradiating face. Inner crystals along with wall crystals multiply particularly within the effectively refined zone and they contribute equally to structure refining. Isothermal holding after ultrasonic melt treatment results in loss of nucleation potency for nearly a half of nuclei, indicating that ultrasound activated heterogeneous nucleation may be as equal important as homogeneous nucleation for ultrasonic induced structure refining.
Key words: grain refinement; ultrasonic; aluminum; solidification