Influence of melt processing with electromagnetic acoustic fields on the structure and properties of Al–Si system alloys

The research on the influence of melt processing with electromagnetic acoustic fields on the structure and properties of binary alloys Al–12%Si and Al–20%Si was conducted. The frequency of electromagnetic field induced in the loop antenna was changed between 500, 1000 and 2000 kHz during the experiments. Melts were processed after their degassing and refining. It was determined that this method of melt processing reduces the average total time of alloy production by 12 %. Short-term treatment of melts with electromagnetic acoustic fields helps to grind main phase alloy components and to improve their mechanical properties. Grinding of α-Al dendrites (from 30 to 22 μm) and eutectic Si crystals (from 13 to 10 μm) was observed while processing Al–12%Si eutectic alloy with a frequency of 500 kHz. At the same time, Al–20%Si hypereutectic alloy treatment with a frequency of 1000 kHz led to reduction of eutectic Si crystals from 8 to 5 μm, and of primary Si crystals – from 90 to 62 μm. Under specified processing conditions the tensile strength of Al–12%Si eutectic alloy increased by 13 %, and elongation – by 17 %, the same mechanical properties of Al–20%Si hypereutectic alloy increased by 9 and 65 % respectively. Based on the studies performed it was concluded that the choice of parameters for Al–Si melt processing with electromagnetic acoustic fields depended on the silicon content in the alloy. The increase in silica concentration needs treatment with the waves of higher vibration frequency. This processing technique allows modifying the fine crystalline structure of alloys and as a result causes an improvement of their mechanical properties. It can be successfully used for the production of fine-grained ligatures and Al–Si system alloys. However, further research is required to determine optimal processing parameters depending on the structure of the original charge and the nature of the alloys.

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