Effect of a high magnetic field on the growth of ε-CuZn5 dendrite during directionally solidified Zn-rich Zn-Cu alloys

The effect of an axial high magnetic field on the growth of ε-CuZn5 dendrite during directionally solidified Zn-rich Zn-Cu peritectic alloys was investigated. Experimental results revealed that the magnetic field caused the deformation of the ε-CuZn5 dendrite and induced the occurrence of the columnar-to-equiaxed transition (CET) of the ε-CuZn5 dendrite. Further, EBSD technology was applied to study the dendrite morphology and crystalline orientation in details. It was found that the regular ε-CuZn5 columnar dendrite formed and was oriented with the < 0001 >-crystal direction along the solidification direction at moderate growth speeds (i.e., 10-50 μm/s). When a high magnetic field was applied, equiaxed grains with various random orientations formed. Further, the magnetic crystalline anisotropy of the ε-CuZn5 crystal was studied. Experimental results showed that the ε-CuZn5 crystal owns a magnetic crystalline anisotropy and the < 0001 >-crystal direction is its easy magnetization axis. Moreover, numerical results indicated that a thermoelectric magnetic force acted on the solid near the liquid/solid interface and increased linearly with the magnetic field. The degeneration and breakup of the ε-CuZn5 dendrites during directional solidification of the Zn-Cu alloys under the magnetic field may be primarily due to the thermoelectric magnetic force acting on the solid.