Cell-to-Dendrite Transition Induced by a Static Transverse Magnetic Field During Lasering Remelting of the Nickel-Based Superalloy

Abstract

The effect of static transverse magnetic field on the microstructure of IN 713C nickel-based superalloy treated by laser remelting (LR) has been investigated. Dendrite microstructure’s transition from cellular to dendritic was observed with the application of a 0.45 T static transverse magnetic field during LR. The white streak structures resulting from thermal stress in the molten pool was found to disappear for the sample treated under magnetic field. The Hartman number (Ha) was calculated and found to be larger than 10, indicating that the damping effect of the static magnetic field on the melt flow was found to be dominant in the present situation. The slowed melt flow is beneficial to the dendritic growth, which may be attributed to the cell-to-dendrite transition during LR. The thermoelectric magnetic force (TEMF) acting on the dendrites was found to destabilize the solid/liquid interface and thus enhance dendritic growth during LR under the magnetic field as well. The EBSD analysis shows that new grains formed in the remelting region when the static magnetic field was applied. The TEMF was calculated to be as high as 1.12 × 106 N/m3, which is capable of fragmentting the dendrite arms and leading to the formation of new grains during LR.