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Research on Grain Refinement in Hypoeutectic Al-Si Alloy during Solidification under an Alternating Electric Current Pulse

1
Shaanxi Key Laboratory of Condensed Matter Structures and Properties and Key Laboratory of Space Applied Physics and Chemistry, Ministry of Education, School of Science, Northwestern Polytechnical University, 127 West Youyi Road, Xi’an 710072, China
2
College of Science, Sichuan Agricultural University, Ya’an 625014, China
*
Authors to whom correspondence should be addressed.
Metals 2019, 9(5), 571; https://doi.org/10.3390/met9050571
Received: 25 April 2019 / Revised: 9 May 2019 / Accepted: 14 May 2019 / Published: 16 May 2019
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Abstract

Experiments on transient directional solidification were carried out to study the columnar to equiaxed transition (CET) in Al-7Si alloy without and with an alternating electric current pulse (AECP). Without AECP, the macrostructure consists of typical columnar and equiaxed zones, separated by a near horizontal plane. As the AECP is applied during solidification, an additional fine equiaxed zone (FEZ) occurs in the as-cast macrostructure. From measured temperature profiles, cooling rate and temperature gradient are determined. It is found that CET occurs for a critical value of the cooling rate, which is observed to be about 0.14 K·s−1 in the present investigation. Furthermore, the macrostructural observation with mold for embedding the mesh plate demonstrates that the major factor responsible for the formation of fine equiaxed grains is the detachment of crystal nuclei from the upper contact surface and the lateral wall. The detachment is in turn ascribed to electric current-associated free energy change (ΔGe)-induced the driving force F. View Full-Text
Keywords: columnar to equiaxed transition; directional solidification; casting; grain refinement; aluminum alloys columnar to equiaxed transition; directional solidification; casting; grain refinement; aluminum alloys
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Li, N.; Zhang, L.; Zhang, R.; Yin, P.; Xing, H.; Wu, H. Research on Grain Refinement in Hypoeutectic Al-Si Alloy during Solidification under an Alternating Electric Current Pulse. Metals 2019, 9, 571.

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