| In this research,the aluminum silicon alloy was solidified under the effect of pulse magnetic field,and the object is to analyze its refinement mechanism in pulse magnetic field.Using pulse magnetic field in the solidification process of industrial pure Al and Al-Si alloy,with the gradual increase of pulse voltage,pure aluminum and Al-Si alloy solidification structure has been well refined.With the increase of Si component,the structure of Al-1Si to Al-2Si is refined and the structure of Al-2Si to Al-7Si is coarsened.Without pulse magnetic field,the solidified structure of pure aluminum and Al-Si alloy are bulky columnar crystal,the solidified structure when applying pulse magnetic field is small isometric crystal.Through the comparative study,found the change from columnar crystal to isometric crystal will not happen immediately after applying pulse magnetic field but waiting for the concentration of equiaxial crystal nucleus reaches a certain number.Pulse magnetic field simulation and the experimental results have been shown that the use of pulse magnetic field in solidification makes the temperature convection and composition convection in metal melt.And the composition convection is the reason why the forefront branch crystal will break into fracture after turning on PMF.This research found that the source of equiaxial crystal nucleus mainly includes: the forefront of columnar dendrites fracture,the deposition of the top branches crystal nucleus and the rupture of solidified shell mold. |
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