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Acta Metall Sin  2018, Vol. 54 Issue (7): 1042-1050    DOI: 10.11900/0412.1961.2017.00421
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Investigation on the Change of Thermoelectric Power of Al-Fe Hypoeutectic Alloy Melt Caused by AC Magnetic Field
Jianfeng ZHANG1, Qing LAN2, Qichi LE2()
1 College of Sciences, Northeastern University, Shenyang 110819, China
2 Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110819, China
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Abstract  

A lot of studies have shown that electromagnetic field can significantly refine the metal solidification structure, thus improve the deformation properties and functional performance of metallic materials. However, the mechanism of how electromagnetic field affects melt structure remains unclear, so an intensive study of the effects of electromagnetic field on melt structure is very important for an in-depth understanding of the essence of melt solidification under external electromagnetic field. The effect of alternating current (AC) magnetic field with different exciting currents, magnetic frequencies and loading time on the thermoelectric potential difference (U) and melt microstructure of Al-0.99%Fe (mass fraction) hypoeutectic alloy at different temperatures was investigated in this work. The results showed that AC magnetic field would lead to a decrease in U of liquid Al-0.99%Fe hypoeutectic alloy. When the magnetic field was removed, the decreased thermoelectric potential difference experienced a rapid recovery process and a poor recovery process to increase to the initial value. The influence of AC magnetic field on U was different at different temperatures. With the increase of the magnetic frequency, the influence of AC magnetic field on U decreased. And the influence of AC magnetic field on U increased with the increase of the exciting current and loading time, however, there was a saturated loading time. There was a correlation between the change of U of Al-0.99%Fe hypoeutectic alloy and the change of size of the primary α-Al phase caused by AC magnetic field, therefore, the change of thermoelectric potential difference could be used to characterize the effect of AC magnetic field on the microstructure of the alloy melt of Al-0.99%Fe hypoeutectic alloy.

Key words:  thermoelectric power      thermoelectric potential difference      AC magnetic field      Al-0.99%Fe hypoeutectic alloy     
Received:  10 October 2017     
ZTFLH:  TG113.12  
Fund: Supported by China Postdoctoral Science Foundation Funded Project (No.2015M571320) and Fundamental Research Funds for the Central Universities (No.N150504002)

Cite this article: 

Jianfeng ZHANG, Qing LAN, Qichi LE. Investigation on the Change of Thermoelectric Power of Al-Fe Hypoeutectic Alloy Melt Caused by AC Magnetic Field. Acta Metall Sin, 2018, 54(7): 1042-1050.

URL: 

https://www.ams.org.cn/EN/10.11900/0412.1961.2017.00421     OR     https://www.ams.org.cn/EN/Y2018/V54/I7/1042

Fig.1  Schematic of the experiment equipment (1—alternating current (AC) power; 2—heating and protection system; 3—excitation coil; 4—sample container; 5—temperature measuring device; 6—data acquisition; 7—dual time relay; 8—resistivity measurement)
Fig.2  Effect of AC magnetic field on the thermoelectric potential difference between two electrodes of Al-0.99%Fe alloy melt (U—thermoelectric potential difference; t—time; ΔU0—the maximum variation of U; ΔU1—the variation of U during fast recovery process; ΔU2—the variation of U during slow recovery process; ΔU3—the residual variation of U; Δt0—the magnetic field treating time; Δt1—the fast recovery time; Δt2—the slow recovery time; Δt—the total recovery time) (a) curve of U to t(b) curve of U, polyfit of U and its' first deriv-ative to t after stopping application of AC magnetic field
Fig.3  Curves of characteristic parameters of thermoelectric potential difference to temperatures (T)(a) curves of ΔU0 and ΔU1 to T (b) curve of ΔU2 to T (c) curve of ΔU3 to T (d) curves of Δt1, Δt2 and Δt to T
Fig.4  Curves of characteristic parameters of thermoelectric potential difference to magnetic frequency (f )(a) curves of ΔU0 and ΔU1 to f (b) curve of ΔU2 to f (c) curve of ΔU3 to f (d) curves of Δt1t2 and Δt to f
Fig.5  Curves of characteristic parameters of thermoelectric potential difference to exciting current (I)(a) curves of ΔU0 and ΔU1 to I (b) curve of ΔU2 to I (c) curve of ΔU3 to I (d) curves of Δt1, Δt2 and Δt to I
Fig.6  Curves of characteristic parameters of thermoelectric potential difference to loading time (Δt0) (a) curves of ΔU0 and ΔU1 to Δt0 (b) curve of ΔU2 to Δt0 (c) curve of ΔU3 to Δt0 (d) curves of Δt1, Δt2 and Δt to Δt0
Fig.7  Solidification microstructures of Al-0.99%Fe alloy quenched from 680 ℃ (a, b), 705 ℃ (c, d), 725 ℃ (e, f) and 765 ℃ (g, h) without (a, c, e, g) and with (b, d, f, h) AC magnetic field
Fig.8  Curves of ΔU3 of Al-0.99%Fe hypoeutectic alloy melt and the change of size of the primary α-Al phase (Δd) caused by AC magnetic field to temperatures
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