Numerical Simulation And Experimental Study On Solidification Of 7A04 Aluminum Alloy Under Rectangular Wave Magnetic Field

The quality of 7A04 aluminum alloy product has an important relationship with the solidification structure of 7A04 aluminum alloy ingot.Therefore,how to efficiently refine the solidification structure of 7A04 aluminum alloy ingot is one of the hotspots in the research of 7A04 aluminum alloy preparation.In this paper,the effects of the rectangular wave magnetic field on the refine solidification structure of the 7A04 aluminum alloy ingot are studied by experiments and numerical simulations,and a new technical scheme for the grain refinement of the 7A04 aluminum al oy semi-continuous ingot is provided.Combined with the existing results,the nucleation process is analyzed,reveals that the electromagnetic energy of the pulse magnetic field can reduce the nucleation activation energy,which is required for the nucleation process,and the energy fluctuation factor of the melt system is improve.With the increase of the nucleation rate in the metal melt.The microstructure of the ingot is refined.Based on the theory of electromagnetic energy,the solidification experiment of 7A04 aluminum alloy was carried out on the experimental platform.The effect of rectangular wave magnetic field on the solidification structure and the solidification curve of 7A04 aluminum alloy was studied.It is found that the rectangular wave magnetic field can effectively refine the solidification structure of the 7A04 aluminum alloy ingot.At the same time,the solidification microstructure of the ingot evolves from a large rose flower shape to a small spherical shape,and the uniformity of solidification structure is obviously improved.The cooling rate of the melt is increased and the solidification equilibrium temperature is lowered.At current equipment conditions,the peak current is 100 A,and the duty cycle is 20%,the best grain refinement can be obtained.The numerical simulation of solidification process of 7A04 aluminum alloy under experimental conditions is carried out with finite element method.The results show that with applying the rectangular wave magnetic field,the entire top of the melt is impacted by electromagnetic energy,and the nucleation rate is greatly improved;the temperature difference in the whole melt is reduced,the temperature field distribution is uniform,and the temperature gradient on the radial section of the melt is reduced.Promotes the formation of equiaxed crystals with rounded grain boundaries.At the same time,the flow field from top to bottom and throughout the melt is formed,which is beneficial to the dispersion of the crystal nucleus,promotes the refinement of the ingot solidification structure,and improves the uniformity of the ingot solidification structure.Besides,the cause of the optimal current parameter is further analyzed by calculating the melt nucleation rate under different current parameters.The 7A04 aluminum alloy semi-continuous casting experiment result show that the rectangular wave magnetic field can effectively refine the solidification structure of the 7A04 aluminum alloy semi-continuous ingot.Compared with the ingot without magnetic field,the grain size at the center of the ingot decreases by 21.73%.The grain size of the side decreased by 14.20%,and the surface quality of the ingot also greatly improved.The cold pits visible to the naked eye are significantly reduced,providing a new technological solution for the grain refinement of the 7A04 aluminum al oy semi-continuous ingot.