Effect of electric pulse and rotating magnetic field on solidification microstructure and properties of Al-Zn-Mg-Cu alloy

The effects of pulse current, pulse frequency, magnetic field current, and magnetic field frequency on the so-lidification microstructure and mechanical properties of Al-Zn-Mg-Cu alloy are studied by applying electric pulse and rotating magnetic field simultaneously during the solidification process. The electromagnetic field and flow field in the solidification process of compound field treatment (electric pulse + rotating magnetic field) are simulated by COMSOL finite element software. The mechanism of refining the solidification structure of Al-Zn-Mg-Cu alloy by compound field treatment is preliminarily clarified. The parameters of compound field treatment are optimized by orthogonal experiment, and it is determined that the magnetic field current and magnetic field frequency are the main factors for obtaining finer grains. The average grain size of the alloy under conventional solidification is 140.3 mu m, which is further reduced to 95.8 mu m by the compound field treatment (pulse current of 700 A, pulse frequency of 30 Hz, magnetic field current of 150 A, magnetic field frequency of 3.5 Hz). The tensile strength of Al-Zn-Mg-Cu alloy increases from 174.5 MPa (conventional solidification) to 211.3 MPa (compound field solidification).