Gas Atomization of Amorphous Aluminum: Part I. Thermal Behavior Calculations |
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Authors: | Baolong Zheng Yaojun Lin Yizhang Zhou Enrique J Lavernia |
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Affiliation: | (1) Department of Chemical Engineering and Materials Science, University of California–Davis, Davis, CA 95616, USA |
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Abstract: | In this article, the thermal history and cooling rate experienced by gas-atomized Al-based amorphous powders were studied
via numerical simulations. Modeling simulations were based on the assumption of Newtonian cooling with forced convection,
as well as an energy balance, which involves gas dynamics, droplet dynamics, and heat transfer between gas and droplet. To
render the problem tractable, phase transformations, crystal nucleation, and growth were not taken into account in the analysis
of the solidification of Al droplets; instead, an energy balance approach was formulated and used. The numerical results and
associated analysis were used to optimize processing parameters during gas atomization of Al-based amorphous powder. The results
showed that the cooling rate of droplets increases with decreasing powder size and can reach in excess of 105 K/s for powder <20 μm in diameter. Gas composition has a more significant influence on cooling rate than gas pressure, and 100 pct He has the
highest cooling effect. The results also showed that the cooling rate increases with increasing melt superheat temperature. |
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