Nd–Fe–B-based anisotropic nanocrystalline hard magnetic alloys

Huy Dan Nguyen, Hai Yen Nguyen, Thi Thanh Pham, Thi Thanh Huyen Nguyen, Huu Duc Nguyen, Dinh Thang Duong, Hoang Long Dinh, Van Duong Nguyen, Dang Thanh Tran, Hong Ky Vu, Khanh Tung Do and Tien Hung Luu

Abstract

Nd_10.5Fe_83.5−xGa_xB₆ (x=1.5, 3 and 4.5) ribbons were prepared by melt-spinning method with various wheel speeds from 5 to 40 m s⁻¹. Strong crystallographic texture with c-axis of Nd₂Fe₁₄Bcrystallites along normal of the ribbon surface was observed. The texture degree can be enhanced by decreasing the quenching rate during solidification of the melt and by increasing the concentration of Ga. Preferred orientation of the nanocrystallites with their size of 10–30 nm is obtained not only by controlling the quenching rate of the melt during solidification but also by appropriately annealing the over-quenched ribbons. The texture of microstructure clearly affects magnetic anisotropy of the ribbons. With increasing concentration of Ga, the magnetic anisotropy of the ribbons is considerably increased. The coercivity above 6.5 kOe and maximum energy products larger than 15 MGOe can be achieved on the ribbons with Ga-concentration of 1.5%