Numerical Simulation Of Solidification Structure Of Aluminum Alloy Under Electromagnetic Stirring

Electromagnetic stirring, characterized by non-pollution, non-contact and precisely controlled with industry, which has been successfully applied in fields of non-ferrous metals and other materials processing. Now much attention is paid to obtain uniformly fine, non-dendrite microstructure during solidification in metal processing. It is considered that the flow field has effect on grain nucleation and growth. So it is of great importance to exposit flow field, temperature field and the tissue distribution and refinement mechanism by electromagnetic stirring for slurry microstructure with high quality. In this paper, the combination of experimental and simulation is used to study the effects of electromagnetic field, flow field, temperature field on solidification structure of Al-5%Cu alloy.(1) The CA-FE model was built through coupling the finite element and cellular automaton method. The finite element method (the ANSYS software) was used to calculate electromagnetic field, and the cellular automaton method was used to simulate solidification microstructure. In microstructure simulation, the nucleation adopts the continuous nucleation model based on Gaussian distribution, and the growth adopts the KGT model to calculate the dendrite tip growth rate. The effects of stirring current, frequency, nucleation parameters, pouring temperature, mold temperature and mold thickness on the temperature field, grain distribution and size are investigated.(2) The temperature field of Al-5%Cu alloy melt under electromagnetic stirring is uniform. The cooling rate of the corner melt is the fastest rate, and the organization is more uniform and fine. With the increase of the stirring current, the magnetic flux density and electromagnetic force gradually increases, the magnetic flux density and electromagnetic force of the corner melt is dropping suddenly, and the cooling rate becomes faster, more uniform temperature field, even smaller organizations. With the stirring frequency increasing, the magnetic flux density and electromagnetic force decreases gradually, the cooling rate is slower, and the microstructure is coarser.(3) With the pouring temperature rising from770℃to690℃without electromagnetic stirring, the grain size increases from385.7μm to512.9μm. Along with the pouring temperature increasing from720℃to690℃under electromagnetic stirring, the grain size reduces from247.2μm to219.4μm. But when the pouring temperature continues to rise to770℃, the grain size increases to262.3μm, and the cooling rate becomes slow. With the mold temperature from room temperature to400℃without the electromagnetic stirring, the cooling rate becomes slow, the proportion of columnar grains decreases, and the grain size decreases from409.2μm to343.7μm. Under the electromagnetic stirring, the cooling rate speeds up, the proportion of columnar grains decreases, and the grain size decreases from281.3μm to225.5μm. With the mold thickness increasing from10mm to20mmwithout electromagnetic stirring, the grains become coarse, the proportion of columnar grains increasing, and the grain size increases from385.7μm to427.3μm. Under electromagnetic stirring, the cooling rate was accelerated. With the mold thickness increasing the cooling rate was accelerated, and the average grain size decreases from247.2μm to163.2μm. Electromagnetic stirring plays a major role in grain refinement.(4) Compared with the simulation and experimental results, under the electromagnetic stirring, the temperature field becomes more uniform. It makes a large number of nuclei form at the same time. The solute does not enrich in the solidification front, reducing the constitutional undercooling. It is in line with the known uniform solidification theory, and to verify the correctness of the model, algorithms and procedures used.