The Effects Of Crucible Shape On Microstructure Of Semisolid Aluminum Alloy In Electromagnetic Stirring Process

Although the development period of electromagnetic stirring technology is very short,it has a great influence on the solidification process and solidification structure of alloy melt,and has the advantages of non-contact,pollution-free,strong controllability and broad application prospect,which has been widely used in the field of manufacturing industry.Grasping the flow law of the semi-solid alloy melt under the action of electromagnetic stirring,studying its influence on the evolution of the solidified structure of the alloy and the refinement of the structure are extremely important for obtaining high-quality slurry and improving the properties of the alloy.The purpose of this paper aims to clarify the influence of electromagnetic stirring parameters and proportion parameters of the major and minor axial ratio of the non-circular crucible on the solidification process and solidification structure of semi-solid A356 aluminum alloy,and to provide technical support for the preparation of semi-solid A356 aluminum slurry with excellent performance.The effect of the major and minor axial ratio of the non-circular crucible on the solid-liquid phase transition of semi-solid A356 aluminum alloy was studied.As the ratio of the major and minor axes of the crucible increases,the time required for complete solidification at the end point of the major and minor axes was decreasing,and the time for complete solidification at the end point of the major and minor axes was less than for the minor axis.Due to the influence of internal heat conduction and thermal convection in the alloy melt,the maximum and minimum temperatures of the melt both showed a downward trend,with a small decline range.With the increase of major and minor axial ratio of the non-circular crucible,the larger of the difference between the maximum and minimum temperatures in the melt increases.When the melt was completely solidified,the aluminum alloy had only heat conduction,and the temperature drop rate of the aluminum alloy was greatly increased.The effects of electromagnetic stirring frequency and current intensity on the electromagnetic field,flow field and temperature field in semi-solid A356 aluminum alloy were studied.With the increase of different current intensities and electromagnetic frequencies,the larger of the maximum electromagnetic force on the major and minor axial ratio of the non-circular crucible,and gradually increased in the radial direction,reaching the maximum value of the electromagnetic force at the crucible radius of 0.8-0.9 times.Beyond this distance,the electromagnetic force began to decrease sharply.Under the condition of constant stirring time,when the electromagnetic frequency was 30 Hz and the current intensity was 5A,the microstructure of the melt reached the best.At this time,the average equal-area circle diameter of the primary phase of the semi-solid alloy was 106.1 ?m,and the average shape factor was 0.72.Based on the research of the appropriate electromagnetic frequency and current intensity,the influence of the major and minor axial ratio of the non-circular crucible on the semi-solid A356-Y alloy was studied.With the increased of the proportion of the major and minor axial ratio,the maximum electromagnetic force on the major axis firstly increase and then decrease,while the maximum electromagnetic force on the minor axis tended to firstly decrease and then increase.When the major and minor axial ratio of the non-circular crucible is 1.3,the maximum electromagnetic force on the major axis reached the maximum value,while the maximum electromagnetic force on the minor axis reached the smaller,and the maximum flow velocity in the aluminum alloy melt was larger than other proportions,and the change rule of the flow velocity difference was consistent with the change trend of the maximum flow velocity on the major and minor axial ratio on the whole,showing the trend of firstly increase and then decline,and the flow velocity difference of the melt reached a larger value when the major and minor axial ratio was 1.3.Through experimental study,the suitable technological parameters for preparing semi-solid A356 aluminum alloy slurry were obtained: the current intensity was 5A,the electromagnetic frequency was 30 Hz,and the major and minor axial ratio was 1.3.