Effect of a high magnetic field on microstructures of Ni-based superalloy during directional solidification

• Directional solidification of superalloy in a high magnetic field has been studied.
• Magnetic field induces columnar to equiaxed transition at lower growth velocity.
• The solid–liquid interface shape was obviously modified in a high magnetic field.
• A refined columnar dendrite structure can be obtained at proper magnetic field.

The effect of a high magnetic field on the dendrite morphology of superalloy DZ417G during directional solidification at a low solidification velocity has been investigated experimentally. It was found that the magnetic field induces columnar to equiaxed transition (CET) and makes the primary dendrite arm spacing decrease. In addition, the magnetic field causes deformation of the solid–liquid interface shape and the macrosegregation in the mushy zone. Based on these results, it was found that both of the thermoelectric magnetic convection (TEMC) and the thermoelectric magnetic force (TEMF) cause CET, the change of solid–liquid interface shape and the formation of macrosegregation. This is in good agreement with predicted values of the TEMC and TEMF, respectively. The primary dendrite arm spacing was changed by the interdendritic TEMC in the magnetic field.