Effect Of Electromagnetic Field On Solidification Process Of Cast Aluminum Alloy

As the most promising metal materials processing technology in the 21 st century, Semi-solid technology has been widely used in many areas. As a important part of the preparation of semi-solid slurry, Electromagnetic stirring has important effects on the solidification process of alloy slurry, and is related to the microstructure morphology of the sample directly. Both ZL203 and 6061 aluminum alloy are researched in this paper, the effects of electromagnetic stirring and rare earth on the solidification process and microstructure morphology are studied.Firstly, the semisolid ZL203 alloy slurry was prepared by a self-made electromagnetic stirring unit with frequency conversion. The morphology and size of α-Al phase were analyzed under the different stirring times and frequencies, and effect of the stepped stirring on the melt was researched by changing the frequency during continuous stirring. The results indicate that the quality of semisolid alloy slurry was effectively improved by stepped stirring, and the suitable technology of stepped stirring for semisolid ZL203 alloy was obtained, which included ZL203 alloy poured at 670℃, and stirred for 5s at 40 Hz, then for 10 s at 30 Hz, and isothermally holding at 620 ℃ for 5min, finally. There was higher quality in semisolid ZL203 alloy ingot, in which the average equal-area-circle grain diameter and average morphology factor of primary α-Al phase at the central and edge position are 85.62, 84.52 μm and 0.86, 0.85, respectively. Moreover, the the mechanisms of grain refinement of the rare earth Er on the microstructure of the alloy under electromagnetic stirring is researched. The result indicates that: Er can refine the grains better when in the form of simple substance Al3 Er than in the form of Er.The semisolid ZL203 alloy slurry was prepared by the electromagnetic stirring with low frequency, and the effect of electromagnetic stirring on the concentration of Cu in Al was researched. ZL203 alloy melt was poured at the different temperature in the solid-liquid phase range, and isothermally stirred. The melt was slowly cooled to below the solidus temperature, then quenched. The results indicated that the concentration of Cu in Al was improved by electromagnetic stirring to decrease the extent of the intergranular segregation in the alloy. There were the certain effects of the poured temperature on the concentration of Cu in Al, in which the concentration increased with the low pored temperature, and the intergranular segregation decreased.Lastly, the slurry of semisolid 6061 Al alloy was prepared by low superheat pouring and electromagnetic stirring, and the effects of pouring temperature and electromagnetic stirring on microstructure of semisolid 6061 Al alloy were researched. The results indicated that there were the great effects of pouring temperature on the microstructure in the alloy, in which the fine grain in the semisolid alloy could be obtained by pouring at 660℃. Morphology of microstructure and size of grain in the semisolid alloy were effectively improved by electromagnetic stirring, in which the better morphology and size of microstructure in the semisolid alloy were gained when the parameters of electromagnetic stirring were electromagnetic frequency 30 Hz and stirring time 15 s. The suitable processing parameters for preparing slurry of semisolid 6061 Al alloy were obtained through the test.