| Electromagnetic stirring technique is not easy to involved in air,contactless and not contaminate the alloy slurry.Operated easily,and can change the flowing state of metals fluid to improve metallographic structure of metals,thus it is widely concerned and applied.Two central parameters of electromagnetic stirring: current and frequency,greatly impact the stirring state of the aluminum alloy slurry so that the metallographic structure of solidified will has a crucial effect.In the process of electromagnetic stirring,sharply change a more obvious electromagnetic stirring parameter : current,triggered a sharply change of the stirring state,as for the effect to metallographic structure if the sharply change of the stirred state cause a secondary breakage in the aluminum slurry and the dendritic crystal were caused by sudden flow and rapid change of the stirring due to Lorentz force has not been considered,and the electromagnetic stirring frequency corresponding to rapid change current has not been explored.At the same time,after heat preservation to semi-solid A356 aluminum alloy slurry,different cooling velocities in the cooling process have not been studied.In this regard,this project explores one of the parameters of electromagnetic stirring: current,having a rapid change and the electromagnetic field,whether the temperature field and flow field of the semi-solid aluminum alloy slurry have something different,with the same time ascertain the optimal electromagnetic stirring frequency that is corresponded to current;and the changes in the temperature field at different water quenching temperatures,besides,the effect to the primary phase by combining computer technology with experimentation.Explored at the same stirring frequency,different stirring current sharply change value on magnetic strength,electromagnetic force and temperature,and flow velocity in aluminum alloy slurry;In the case of the same stirring current rapid change value,the effect of different electromagnetic stirring frequencies on magnetic strength and electromagnetic force in aluminum alloy slurry.The results showed that with the same stirring frequency,as the electromagnetic stirring current is increased,the magnetic strength,electromagnetic force and flow velocity of the aluminum alloy slurry are increased,when the current value is increased from 2A to 6A,magnetic strength,electromagnetic force and flow velocity reached the maximum.As the electromagnetic stirring current is constantly increasing,the temperature field in the slurry is increasingly distributed even more homogeneous due to the electromagnetic force;the same stirring current rapid change value,with the electromagnetic stirring frequency increased,the magnetic strength and electromagnetic force of the aluminum alloy slurry have increased and then decreased,in which the magnetic strength and electromagnetic force reached the maximum when the electromagnetic stirring frequency is 25 Hz..The primary phase of the semi-solid aluminum slurry achieves the best when electromagnetic stirring parameters are: the current is increased from 2A to6 A,and the frequency is 25 Hz.At this time,the mean equal circle diameter of the primary phase was about 117.9?m,and the shape factor was about 0.71.On the basis of the optimal electromagnetic stirring frequency obtained and the rapid change stirring current by the previously derived the effect of the water quenching were carried out at 30?,50?,70? and 90? to the alloy slurry temperature and the primary phase was explored.The results showed that with the raise of water temperature,the decreasing rate of melt temperature showed a slowing trend.In four cases,the temperature drop fastest at 30?,the temperature drop the slowest at 90?.The primary phase of the aluminum alloy will optimize first and then deteriorate with the increase of temperature.Where in the water quenching temperature is 70?,the primary phase reached the best,and the mean equal circle diameter was about 114.4 ?m,at the moment the shape factor was about 0.74 at this time. |
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