Effects Of High Magnetic Field On Directional Solidification Of Succinonitrile

A transparent simulated alloy directional solidification device with controllable temperature gradient under high magnetic field is designed and fabricated in this work.The succinonitrile?SCN?with 99.927%purity was chosen as the experimental material.The growth morphology of the samples was observed in the absence of magnetic field conditions and imposition of magnetic field.The growth rate,dendrite spacing,tip radius and other main characteristics parameters were measured under different temperature gradient as well as and magnetic field strength,thus the SCN directional solidified microstructure formation and evolution under the magnetic field were theoretically analyzed.In the absence of magnetic field conditions,the directional solidification structure of the SCN transparent alloy is oblique dendrites,the secondary dendrites on both sides of the growth tips are asymmetric,and the secondary dendrites of the SCN in the opposite direction to the heat flux are larger.With the increase of magnetic field strength,the growth morphology of the SCN obviously changed during the directional solidification,and the cellular crystal,dendritic crystal,oblique dendritic crystal and seaweed crystal appeared respectively.In the absence of magnetic field conditions,the growth rate of SCN in the observation area changed little with the different temperature gradient,which showed the opposite trend with the degree of undercooling.Under the same temperature gradient,the directional solidification growth rate of SCN decreases with the increase of magnetic field.The application of high magnetic field significantly inhibits the growth of SCN.In the absence of magnetic field conditions,the primary dendrite spacing and secondary dendrite arm spacing of SCN decrease with the increase of temperature gradient.With the increase of the magnetic field strength,the temperature gradient is 3K/mm,and the primary dendrite spacing decreases.When the magnetic field strength is1T,the primary dendrites in the other temperature gradients are larger than those in the absence of magnetic field.In the absence of magnetic field conditions,the growth rate of the SCN was?₁?V^k,k?0.86 at different temperature gradients.Under the same temperature gradient,the k value decreased with the increase of the magnetic field intensity.In the absence of magnetic field,the value of the tip radius of SCN increases with the increase of temperature gradient.At the same temperature gradient,the tip radius of the growth of SCN increases with the increase of the magnetic field.In summary,under the influence of a high magnetic field,the directional solidification of SCN reduces the growth rate,the dendrite arm spacing and the secondary dendrite arm increase,and the tip radius increases and the grains coarsen.The reason should be that the high magnetic field causes the increase of the melting entropy of SCN,which in turn leads to the increase of the value of?in the Jackson factor,the smaller total number of layers in the solid-liquid interface and the decrease of the number of liquid atoms to the solid phase,The growth rate decreases;the primary dendrite spacing is inversely proportional to the product of the crystal growth rate and the temperature gradient.With the increase of the intensity of the high magnetic field,the growth rate is lower and the distance between the primary arms increases with the temperature gradient unchanged.The tip radius is inversely proportional to the dendrite growth rate.Under the same temperature gradient,the strength of the high magnetic field increases,the growth rate decreases,and the radius of the tip of SCN increases.