Microstructure characteristics and effect of grain orientation on magnetic properties of Fe₆₃Co₃₂Gd₅ alloy ribbons

Abstract

By using the melt spinning techniques, the Fe₆₃Co₃₂Gd₅ alloy ribbons with 15-50 m in thickness and 3-7 mm in width were prepared at the wheel speeds of 15, 20, 25 and 35 m/s. The rapid solidification microstructures were characterized by three layers, the middle layer of which reaches 80% thickness and forms the column grain of (Fe,Co) solid with Gd solution. Grain refinement takes place with the increase of the wheel speed. And after 0.5 h heat treatment at 823 K, the ribbon thickness becomes larger and the middle layer of column grain is very orderly perpendicular to the ribbon plane. The coercivity of quenched and annealed Fe₆₃Co₃₂Gd₅ ribbons both have the inflection point at the wheel speed of 20 m/s, and the tendency is declining. The heat treatment processing makes the coercivity become lower by improving the order of (Fe,Co)₁₇Gd₂ compound. The saturation magnetization of quenched ribbons increases with the enhancement of wheel speed, whereas that of annealed ones decreases firstly and then increases. The minimum coercivity is 5.30×10³ A/m and the maximum saturation magnetization is 163.62 A·m²/kg, which is obtained in the conditions of the wheel speed of 35 m/s and 0.5 h heat treatment at the temperature of 823 K.

Keywords

Fe-Co-Gd alloy ribbon / rapid solidification / phase composition / magnetic properties

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