| Electromagnetic stirring can significantly affect the flow state of molten aluminum alloy.However,there are still some deficiencies in researchers' understanding of the rule of melt flow,distribution of temperature field and diffusion of solute in semi-solid aluminum alloy melt.The temperature field and flow field during solidification of semi-solid Aluminum Alloy have great influence on the final aluminum alloy.In the past research of electromagnetic stirring technology,most of the electromagnetic stirring methods used were unidirectional continuous electromagnetic stirring,in order to get better heat and mass transfer effect,the electromagnetic stirring mode can be changed during the preparation of semi-solid aluminum alloy slurry.However,it is difficult to reveal the effects of different electromagnetic stirring methods on the flow and temperature of semi-solid aluminum alloy solution by traditional solidification theory or experimental methods.In this paper,the temperature and flow field in semi-solid aluminum alloy melt under complicated electromagnetic stirring conditions are studied by numerical simulation and experiment.In the process of preparing high quality semi-solid A356 aluminum alloy by electromagnetic stirring,the effects of different electromagnetic frequency,current intensity and stirring mode on the quality of semi-solid alloy slurry were systematically studied.By changing the electromagnetic stirring parameters and controlling the electromagnetic stirring process,the flow rate of the alloy melt is increased and the temperature field in the melt is homogenized,so that the alloy melt is in the optimal solidification environment;By adding rare earth and changing the electromagnetic stirring method,the eutectic reaction in the alloy melt is increased,the melt flow rate is changed,the effective nucleation rate is increased,and the electromagnetic stirring effect is better.In this paper,the numerical simulation method is validated by experiments,and the effects of electromagnetic stirring parameters and mode on electromagnetic field,flow field,temperature field and solidification structure of semi-solid A356 aluminum alloy are systematically studied.The effects of different stirring parameters on the maximum velocity of magnetic induction,electromagnetic force and semi-solid aluminum alloy melt were studied by using two-dimensional numerical model and three-dimensional numerical model of magnetic field,and the effect on the morphology of the primary phase.The results show that the electromagnetic force in the alloy melts increases gradually from the inside to the outside due to the wrinkling effect,and the magnetic induction presents the characteristics of "small center and large edge" with the increase of electromagnetic frequency,at the Radial Direction of the Crystallizer 0.8R-0.85 R,at the frequencyof electromagnetic stirring 25 Hz,current 4A and stirring time 12 s,the melt flow velocity is the largest,and at the constant temperature of semi-solid A356 alloy after casting at 650?,the best morphology of the primary phase was obtained when the electromagnetic stirring parameters were30 Hz and 4A for 12 s and kept at 590 ? for 10 min.The average diameter of the equal circle and the average shape factor were 80.6?m and 0.78 respectively.Based on the maximum electromagnetic force in the melt under different electromagnetic stirring parameters,a two-dimensional temperature field model was established by using numerical simulation technique,the effects of one-way continuous electromagnetic stirring and different stirring parameters on the temperature distribution and the morphology of primary phase in semi-solid A356 aluminum alloy melt were investigated.The results show that when the current is small,the electromagnetic frequency increases and the temperature difference decreases gradually,and the temperature difference is the smallest at 4A and 30 Hz,when the temperature difference is0.826 ?,the temperature difference is the smallest at 5A and 25 Hz,the temperature difference is0.837 ?,and the temperature field is the most uniform at 30 Hz and 4A,which is beneficial to grain refinement.The morphology of primary phase of semi-solid A356 aluminum alloy cast at650? was the best when the electromagnetic stirring parameters were 30 Hz and 4A for 12 s,the average diameter of equal circle was 73.5?m,and the average shape factor was 0.79.The effects of different stirring methods on the melt flow field and the solidification structure of the alloy were investigated under the same stirring parameters.The results of numerical simulation and experiment show that the effect of forward turning 6s,reverse turning 6s is better than that of forward turning 12 s and forward turning 6s,stop 1s and reverse 6s.A new process for preparing semi-solid slurry of aluminum alloy and its preparation parameters were formed and perfected.When the aluminum alloy melt was poured into the casting mould at 650?,at 4A,30 Hz,the maximum flow velocity of molten aluminum alloy was obtained under the condition of12 s forward rotating for 6s and reverse rotating for 6s,when the maximum flow velocity of molten aluminum alloy was 82 mm/s on x axis,72.5 mm/s on y axis and 45.6 mm/s on z axis.The average circle diameter and average shape factor of the primary phase are 59.3?m and 0.84 respectively. |
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