Abstract: A new technique termed surface electromagnetic pulse was developed for refining the solidification structure of the 7A04 super-hardness aluminum alloy. The effect of pulsed electromagnetic field on solidified microstructure, crystal orientation and cooling curves were investigated in order to explore the mechanism of microstructure evolution. The experimental results showed that the solidified structure was modified following rules of refining and spheroidization→coarsening and randomization with the increase of magnetic flux density, and a 40% reduction in grain size could be achieved when the increase of magnetic flux density was 241 mT. Magnetic rotation of crystals in size of 225 nm—100 μm could be controlled due to crystal magnetic anisotropy which caused by magnetic energy difference, forming the pulse magnetic preferred orientation. Meanwhile, a good result for grain refinement could also be obtained by the pulse electromagnetic inoculation treatment. It can be explained that the fraction of solid in the melt which was decreased by solidification initial temperature rise was benefit for particle motion.
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2018, Vol. 32 
