Effect of Intermittent Direct Current Magnetic Field on Solidification Microstructure and Properties of Al-5Mg-3Zn-1Cu Alloy

The solidification of Al-5Mg-3Zn-1Cu alloy was treated by intermittent direct current magnetic field under 30% duty cycle and different direct current voltages (0-300 V) and discharge frequencies (0-20 Hz). The effect of intermittent direct current magnetic field on solidification microstructure and mechanical properties of the alloy was studied. The results show that applying intermittent direct current magnetic field effectively refined the solidification structure of the alloy. The primary α-Al phase changed from coarse dendrites without magnetic field to fine rose-like grains, and the second phase changed from coarse and continuous grid structure to fine and discontinuous distribution structure. With the increase of direct current voltage, the grain size, the second phase volume fraction and length of the alloy decreased, and the compressive strength and fracture strain increased first and then decreased. With the increase of discharge frequency, the grain size, the second phase volume fraction and length decreased first and then increased, and the compressive strength and fracture strain increased first and then decreased. After applying intermittent direct current magnetic field, the tensile properties of the alloy were improved, the quasi-cleavage surface decreased in number, and the tearing edge increased in number. When the direct voltage was 200 V, and the discharge frequency was 5 Hz, the compressive sthength and fracture strain were the largest, which increased by 31.6% and 43% compared with those without magnetic field, and the tensile strength and percentage elongation after fracture increased by 79.7% and 83.3%, respectively.