Journal
INTERNATIONAL JOURNAL OF MATERIALS RESEARCH
Volume 108, Issue 6, Pages 465-476Publisher
CARL HANSER VERLAG
DOI: 10.3139/146.111505
Keywords
Al-Si-Mg-RE (RE = Ce; Sc) alloys; Diffusion; Atomic mobility; Solidification; A357 alloy
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Funding
- National Natural Science Foundation of China [51474239]
- National Key Research and Development Program of China [2016YFB0301101]
- Sino-German Center for Promotion of Science [GZ 1208]
- State Key Laboratory of Powder Metallurgy Foundation, Central South University, Changsha, China
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This paper first provides a critical review of experimental and theoretically-predicted diffusivities in both liquid and fcc Al-Si-Mg-RE (RE = Ce, Sc) alloys as-reported by previous researchers. The modified Sutherland equation is then employed to predict self-and impurity diffusivities in Al-Si-Mg-RE melts. The self-diffusivity of metastable fcc Sc is evaluated via the first-principles computed activation energy and semi-empirical relations. Based on the critically- reviewed and presently evaluated diffusivity information, atomic mobility descriptions for liquid and fcc phases in the Al-Si-Mg-RE systems are established by means of the Diffusion-Controlled TRAnsformation (DICTRA) software package. Comprehensive comparisons show that most of the measured and theoretically-predicted diffusivities can be reasonably reproduced by the present atomic mobility descriptions. The atomic mobility descriptions for liquid and fcc Al-Si-Mg-RE alloys are further validated by comparing the model-predicted differential scanning calorimetry curves for RE-containing A357 alloys during solidification against experimental data. Detailed analysis of the curves and microstructures in RE-free and RE-containing A357 alloys indicates that both Ce and Sc can serve as the grain refiner for A357 alloys, and that the grain refinement efficiency of Sc is much higher.
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