Effect of the Solidification Conditions on the Microstructures of AlSi₇Mg Alloy during Semi-solid Remelting

The effect of the solidification conditions on the microstructures was studied during partial remelting of AlSi₇Mg alloy with the help of an electrical pipe-type furnace. The results show that the eutectic is remelted above all and α phases are gradually evolved into spheroidal shape, if the AlSi₇Mg alloys stirred strongly by rotating electro-magnetic field during the first solidification are heated again to 589℃ or 597℃ and have been held for a short time(for example, 5~10 min), and moreover, the higher the holding temperature, the faster the eutectic remelting process and α phase's evolution are. In contrast, even though the AlSi_7 Mg alloy's samples non-stirred with fine dendritic microstructures ate heated to the same temperatures as those stirred by rotating electromagnetic field and have been held for 60 min, it is not possible to change all the dendritic α phases to speroidal α phase.