中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 26 No. 12 December 2016 |
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. New Electrical Materials and Microelectronics Department, Global Energy Interconnection Research Institute, Beijing 102211, China;
3. State Key Lab of Advanced Power Transmission Technology, Beijing 102211, China;
4. State Grid Liaoning Electric Power Supply Co., Ltd., Shenyang 110006, China）
Abstract:The effect of Hf on the grain refinement of as-cast aluminum was investigated using optical microscopy, electron microscopy and X-ray diffraction. The result shows that the grain size of studied alloy decreases effectively with the addition of Hf, Hf can react with Al to form Al3Hf particles during the solidification, the primary Al3Hf particles are highly potent nucleants for Al and the nanoscale coherent Al3Hf particles can inhibit the grain growth by pinning effect. The grain refinement mechanism of studied alloys was verified by the solute theory and the crystallography study, and it can be divided into two distinct types: At low Hf contents, there are no primary Al3Hf phases to form, the acquired grain refinement is primarily attributed to the constitutional undercooling induced by the Hf solute. At medium and high Hf contents, both Hf solute and Al3Hf particles contribute to the refinement.
Key words: grain refinement mechanism; aluminum alloy; casting; Hf; Al3Hf
