The Study On Faceted-Nonfaceted Growth Transition Of Mn-Sb Alloy Under High Magnetic Field

High magnetic field acting on the molten metal will produce a series of effects,such as:Lorentz force,magnetic force and interaction between the magnetic dipoles.The solid-liquid interface,orientation and magnetic properties will be affected when high magnetic field acts on the solidification of molten metal,leading to the transformation between faceted and nonfaceted in the primary phase,and new materials which are strong isotropy were gain.In this paper,Mn-97%Sb hypereutectic alloy with the Sb primary phase is studied,and different high magnetic field is applied to the solidification process,the evolution of the faceted phase was studied and theoretical analyzed according to the microstructure,orientation and magnetic properties of samples,and the following conclusions were gain:(1)Under the condition of furnace cooling for samples,the primary phase always appear nonfaceted in different high magnetic fields.However,different magnetic fields obviously affect on the orientation,especially at the magnetic field of 8.8T,the diffraction peak of(104)plane was obviously strengthened.(2)Under the condition of slow cooling for samples,the faceted primary phase was observed in solidified structure when no magnetic field applies,and the globular and rodlike primary phase when magnetic field applies.Obviously,the faceted primary phase is suppressed by magnetic field and only few faceted phase distributes in structure.The magnetic field shows more significant effects on the orientation comparing with condition of furnace cooling.But the preferred orientation in the<104>direction is the same as in the furnace cooling at 8.8T.(3)According to the analysis of quenched structure under condition of slow cooling,the magnetic field increased the undercooling in the process of solidification,and reaching the peak at the range from 2.2T to 5.5T,the same results about undercooling appear in Ni-21.4%Si eutectic experiments under high magnetic field.The undercooling is the dominant factor which decides whether the primary phase is faceted.The effect of the processing of magnetic field acting on the faceted phase is divided into three stages:primary phase growth and eutectic phase growth:the first stage is nucleation,Lorentz force and thremoelectromagnetic force cause the difference in undercooling.Further more,the dendritic faceted primary phase gradually increases but normal faceted primary phase decrease,and the magnetic field has almost no influence on the orientation with the increase of the magnetic flux density.The last,the faceted phase gradually change into nonfaceted phase,and the effects of the magnetic field acting on the crystal orientation occur at this stage.