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Microstructure evolution of gas-atomized Fe–6.5 wt% Si droplets

Published online by Cambridge University Press:  13 February 2014

Kefeng Li ,
Changjiang Song ,
Qijie Zhai ,
Mihai Stoica  and
Jürgen Eckert
Kefeng Li
Affiliation:
Department of Metallurgical Engineering, School of Materials Science and Engineering, Shanghai University, Shanghai 200072, People’s Republic of China; and Institute for Complex Materials, Institute for Solid State and Materials Research Dresden, Dresden D-01069, Germany
Changjiang Song*
Affiliation:
Department of Metallurgical Engineering, School of Materials Science and Engineering, Shanghai University, Shanghai 200072, People’s Republic of China
Qijie Zhai
Affiliation:
Department of Metallurgical Engineering, School of Materials Science and Engineering, Shanghai University, Shanghai 200072, People’s Republic of China
Mihai Stoica
Affiliation:
Institute for Complex Materials, Institute for Solid State and Materials Research Dresden, Dresden D-01069, Germany
Jürgen Eckert
Affiliation:
Institute for Complex Materials, Institute for Solid State and Materials Research Dresden, Dresden D-01069, Germany; and Dresden University of Technology, Institute of Materials Science, Dresden D-01062, Germany
*
a)Address all correspondence to this author. e-mail: riversxiao@163.com
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Abstract

The magnetic Fe–6.5 wt% Si powder was produced by gas atomization and its microstructure was also investigated. The secondary dendritic arm spacing (SDAS) is related to the droplet size, ${\rm{\lambda }} = 0.29 \cdot {D^{0.5}}$, and the numerical solidification model was applied to the system, giving rise to the correlation of microstructure to the solidification process of the droplet. It is found that the solid fraction at the end of recalescence is strongly dependent on the undercooling achieved before nucleation; the chances for the smaller droplets to form the grain-refined microstructures are less than the larger ones. Furthermore, the SDAS is strongly influenced by the cooling rate of post-recalescence solidification, and the relationship can be expressed as follows, ${\rm{\lambda }} = 74.2 \cdot {\left( {\dot T} \right)^{ - 0.347}}$. Then, the growth of the SDAS is driven by the solute diffusion of the interdendritic liquids, leading to a coarsening phenomenon, shown in a cubic root law of local solidification time, ${\rm{\lambda }} = 10.73 \cdot {\left( {{t_f}} \right)^{0.296}}$.

Keywords

Fe–Si alloysatomizationsolidification microstructuresSDAScooling rate
Type
Articles
Information
Journal of Materials Research , Volume 29 , Issue 4 , 28 February 2014 , pp. 527 - 534
Copyright
Copyright © Materials Research Society 2014 

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References

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