Effect of Magnetic Field Strengths on Microstructure and Properties of Al-7Si-0.3Mg-1Fe Alloy

XU Jie; FENG Xiaowei; SONG Bin; WANG Bing; MAO Hongkui

doi:10.3969/j.issn.1674-6457.2026.05.014

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Journal of Netshape Forming Engineering ›› 2026, Vol. 18 ›› Issue (5) : 149-160. DOI: 10.3969/j.issn.1674-6457.2026.05.014

Iron and Steel Forming

Effect of Magnetic Field Strengths on Microstructure and Properties of Al-7Si-0.3Mg-1Fe Alloy

XU Jie¹, FENG Xiaowei¹, SONG Bin², WANG Bing², MAO Hongkui^1,*

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Abstract

The work aims to systematically explore the effects of different magnetic field strengths on the microstructure, grain size, and mechanical properties of Al-7Si-0.3Mg-1Fe alloy, with focuses on analyzing the regulatory effect of the magnetic field on the morphology of iron rich phases and their distribution patterns, to reveal the mechanism of electromagnetic pump technology in deep iron removal and performance optimization of aluminum alloy, and provide a theoretical basis for the development of efficient and environmentally friendly aluminum alloy purification processes. A direct current electromagnetic pump casting system was used. After casting, the ingot was cut longitudinally, and samples were taken from the top (N region), middle, and bottom (S region). The microstructure and iron rich phase morphology were observed and analyzed by metallographic microscope (OM), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS); The phase composition was identified by X-ray diffraction (XRD); The mechanical properties of alloys (yield strength, tensile strength, and elongation) were tested with a universal tensile testing machine; The grain size distribution was qualitatively analyzed by Image Pro Plus software. When the magnetic field strength increased from 150 mT to 200 mT, the iron rich phases in the middle region transformed from needle shaped β-AlFeSi phases to fishbone shaped α-AlFeSi phases; Under the condition of 300 mT, the iron rich phases in the N-pole and S-pole regions further evolved into block shaped β-AlFeSi phases. The distribution of Fe elements was significantly regulated by the magnetic field: the Fe content in the two pole regions (N and S poles) was enriched with increasing magnetic field strength (up to 1.25% at 300 mT), while the Fe content in the middle region decreased (down to 0.44% at 300 mT). The average grain size increased with the increase of magnetic field strength: the average size was about 490 μm at 150 mT and increased to about 660 μm at 300 mT. The magnetic field enhanced the non-uniformity of grain size distribution, and the phenomenon of grain coarsening in the polar region was more significant (at 300 mT, the proportion of grain size>800 μm in the S region reached 35%). The tensile strength increased from 173.89 MPa at 150 mT to 210.67 MPa at 300 mT (an increase of approximately 21%); The yield strength increased from 69.90 MPa at 150 mT to 80.10 MPa at 300 mT. The comprehensive mechanical performance index (Q value) increased from 256.60 MPa at 150 mT to 284.59 MPa at 300 mT, indicating that magnetic field strengthening significantly improved the bearing capacity of the alloy. In conclusion, the increase in magnetic field strength effectively regulates the morphological evolution and distribution of iron rich phases in Al-7Si-0.3Mg-1Fe alloy, while promoting grain coarsening. This process significantly improves the mechanical properties of the alloy, especially the tensile strength and yield strength. Research has shown that electromagnetic pump technology provides a feasible technical path for efficient iron removal and performance enhancement of Al-7Si-0.3Mg-1Fe alloy by directional migration of Fe elements and optimization of the solidification process.

Key words

DC electromagnetic pump / magnetic field strength / rich iron phase / grain size / mechanical property

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XU Jie, FENG Xiaowei, SONG Bin, WANG Bing, MAO Hongkui. Effect of Magnetic Field Strengths on Microstructure and Properties of Al-7Si-0.3Mg-1Fe Alloy[J]. Journal of Netshape Forming Engineering. 2026, 18(5): 149-160 https://doi.org/10.3969/j.issn.1674-6457.2026.05.014

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