Phase Field Modeling Of Eutectic Growth Undering Forced Convection

The eutectic lamellar is a common organization phenomenon in the solidification of the alloy,the solidification process of the actual alloy is three-dimensional,the results of the simulation of two-dimensional phase-field model are not to represent completely the microstructure of eutectic solidification.There is no doubt that convection exists in the process of solidification of alloys,on the one hand,the transport of mass and heat in melt liquid depend on diffusion,on the other hand,it is seriously affected by liquid flow,the flow of metal liquid significantly changes the distribution of solute field during solidification,the process of eutectic growth is changed directly,so that the microstructure of eutectic lamellar is completely different from diffusion.The mechanical properties depend on the microstructures in solidification.Therefore,it is a significant research topic to study the morphology evolution of three-dimensional eutectic growth under the flow field.In this paper,The numerical simulation method of coupling the phase field method with the LBM model of the numerical simulation method is used,taking CBr4-C2Cl6 as an example,the problem of morphology evolution of three-dimensional(3D)eutectic growth on the condition of the forced convection during isothermal solidification are investigated.The major research works and conclusions are as follows:(1)In the condition of isothermal solidification,the liquid flow significantly changed the growth morphology of lamellar eutectic,the growth mode of periodicity and alternate,which is perpendicular to the solid-liquid interface ?the growth mode of growing to liquid flow direction and heterogeneous nucleation in front of the interface;Liquid flow accelerates the growth rate of eutectic structure.(2)In different fluid flow direction,the growth morphology of the lamellar eutectic structure is obviously different: without flow,the growth mode of the lamellar eutectic is mirror symmetry,which is always perpendicular to the solid-liquid interface;when the angle ?=0obetween the direction of liquid flow and the Y direction(parallel to the eutectic lamellar),liquid flow has no effect on eutectic growth morphology;when the angle ?=45oand ?=90o,the growth mode of the lamellar eutectic is oscillatory instability?? phase nucleation and ? phase branching in front of the interface and grow to liquid flow direction;In contrast to when the angle ?=90o,when the angle ?=45oearlier has the phenomenon of lamellar spacing decreases and lamellar pairs increase due to spacing adjustment.(3)With increasing flow velocity,the velocity of lamellar eutectic growth is faster and occurs more obviously in the direction of liquid flow.The change of the initial interface undercooling is positively correlated with the growth rate of the lamellar,and is negatively correlated with the lamellar spacing;with increasing undercooling,under the effect of solute diffusion and flow field,the eutectic lamellar can be adjusted to stable growth by nucleation and branching.(4)When hypoeutectic and hypoeutectic composition,with increasing initial lamellar spacing: without flow,the growth morphology of eutectic lamellar changes as follows:symmetrical growth and perpendicular to the solid-liquid interface to stable growth? low amplitude oscillatory instability? Large oscillatory instability;With liquid flow,the growth morphology of eutectic lamellar changes as follows: grow to liquid flow direction and low amplitude oscillatory instability? heterogeneous nucleation and branching in front of the interface once ? oscillatory instability and grow to liquid flow direction ?heterogeneous nucleation and branching in front of the interface many times ? oscillatory instability and growth along different slopes.It follows that,when hypoeutectic and hypoeutectic composition,the growth morphology of eutectic lamellar changes are consistent with the change of the initial lamellar spacing.when eutectic composition,with increasing lamellar spacing: without flow,the growth morphology of eutectic lamellar changes as follows: stable growth? low amplitude oscillatory instability? Large oscillatory instability? Rod;With liquid flow,the growth morphology of eutectic lamellar changes as follows: grow to liquid flow direction and low amplitude oscillatory? heterogeneous nucleation and branching in front of the interface once?oscillatory instability? grow to liquid flow direction and large amplitude oscillatory.(5)In qualitative aspect,the simulation results of this paper are basically consistent with those obtained by experiments,and the reliability of numerical simulation results is verified.