Three-dimensional Numerical Simulation Of Melt Convection In Detached Solidification Under Cusp Magnetic Field

Detached Bridgman solidification is a competitive method of crystal growth,combining the advantages of both Bridgman and Czochralski methods. Due to theabsence of the stress produced by differential thermal contraction of the crystal andampoule, detached solidification has outstanding performance in the growth ofheat-sensitive crystal, such as CdZnTe crystal. Additionally, detached solidification is acrystal growth method from the melt, therefore, the melt flow induced by the gradient ofsurface tension is one limiting factor that has a fundamental influence on the crystalquality during the process of detached solidification. Under the condition of gravity, theexistence of buoyancy convection complicates the convection and increases thedifficulty of detachment. In order to control the melt flow, this paper studies theinhibition effect of magnetic field on melt flow by the methods of numerical simulations.The numerical results can provide theoretical guidance for detached solidification ofCdZnTe.The three-dimensional physical model and governing equations for detachedsolidification of CdZnTe crystal are established with the application of cusp magneticfield(CMF). The effect of cusp magnetic field on the thermal field and melt flow arestudied numerically. Meanwhile, the effect of gap width on the melt flow is discussed.The results of cusp magnetic field, axial magnetic field and their resultant magneticfield were carried out to figure out the effect of different types of magnetic field on themelt flow.The numerical results indicate that：1) Under the condition of microgravity, themelt flow becomes weaken and the isotherm distribution is more uniform with theapplication of cusp magnetic field. The inhibition effect of cusp magnetic field on themelt flow is enhanced with increasing magnetic field intensity. The velocity on the freesurfaces decrease and the nonlinearity of temperature distribution reduces as theHartmann number increases. And the critical Marangoni number increases withincreasing Hartmann number.2) Under the condition of gravity, the cusp magnetic fieldhas suppression effect on the melt thermocapillary-buoyancy convection and thevelocity on the free surfaces decreases with an increase of the Hartmann number.Compared with the situation of microgravity, the melt flow is weakened and the criticalMarangoni numbers increase under gravity. Meanwhile, the critical Marangoni number is increased with the Hartmann number increases.3) Both the melt flow and the velocityon the free surfaces decrease with the increase of the gap width.4) By comparing thesuppression effect of cusp magnetic field, axial magnetic field and their resultantmagnetic field, it is found that the suppression effect of resultant magnetic field is mosteffective and the cusp magnetic field is the least.