On the optimization of solidification structures and magnetic properties of Nd70Cu30–50 wt% Nd2Fe14B alloys by electromagnetic vibration

Highlights: • Influences of AC, temperature, and electrode materials on structures and magnetic properties were examined. • Solidification mechanism was proposed when considering the influences of processing parameters. • The optimum condition to segment and align Nd₂Fe₁₄B platelets is determined when EMV is imposed. • The improved magnetic properties with a strong anisotropy in magnetism were achieved. -- Abstract: In the present study, we reported on the optimization of processing conditions under which the developed Nd₂Fe₁₄B laths could be finely segmented and well aligned and thus to form a magnet with a strong anisotropy in magnetism. The starting ingot was the Nd₇₀Cu₃₀–50 wt% Nd₂Fe₁₄B alloy, which was solidified under different conditions when electromagnetic vibration (EMV) was imposed. Solidification structures were observed and magnetic properties were measured in the specimens processed at various states, i.e., electric currents at J = 120 A and J = 90 A, target imposition temperatures at T = 850 °C and T = 700 °C, and electrode materials of C and Fe. The crystallographic orientations of Nd₂Fe₁₄B platelets were revealed by the electron backscatter diffraction (EBSD) technique and the composition of the phase of interest was diagnosed using energy-dispersive X-ray spectroscopy (EDS) attached to an electron scanning microscope (SEM). The phase structures were characterized using X-ray diffraction (XRD) and the magnetic properties of specimens were measured using a vibrating sample magnetometer (VSM). Based on the analysis and measurements presented above, influences of the imposition parameters on solidification structures and routes were discussed, and thus the optimum imposition condition was determined, under which finely segmented and well aligned Nd₂Fe₁₄B platelets could be achieved.