Thermal Stability and Magnetic Properties of Fe–Nd–Al Amorphous Alloys

Abstract

Iron-rich Fe₅₀Nd_50−xAl_x (x=5, 10, 15, 20 at%) alloys were produced by copper mold casting and melt-spinning in order to examine the formation of amorphous alloys. The bulk amorphous cylinders with diameters up to 1.5 mm have been obtained for the Fe₅₀Nd₃₅Al₁₅ alloy. The crystallization temperature (T_x) and melting temperature (T_m) of the alloy are 774 and 880 K, respectively. Accordingly, the temperature interval of T_m and T_x, ΔT_m (=T_m–T_x), is calculated to be 106 K, and the reduced crystallization temperature (T_x⁄T_m) is 0.88. The small ΔT_m and high T_x⁄T_m values are presumed to be the origin for the achievement of the high amorphous-forming ability of the Fe–Nd–Al alloy. The bulk amorphous cylinder exhibits semi-hard magnetic properties at room temperature, i.e., 0.117 T for remanence and 50 kA/m for intrinsic coercive field for Fe₅₀Nd₃₅Al₁₅ alloy with a diameter of 1.5 mm. Moreover, soft to hard magnetic transition between the ribbon and bulk specimens was observed in the Fe-rich Fe–Nd–Al alloys. The semi-hard magnetic properties for the Fe-rich Fe–Nd–Al amorphous alloys with high amorphous-forming ability are promising for future progress as a new type of Fe-based magnetic material.