Structure and magnetic properties of stoichiometric and RE-rich NdY-Fe-B alloy ribbons

Abstract

Here we study the effect of rare earth (RE) contents on melt-spun and annealed NdY-Fe-B alloys, aiming to illustrate their phase structure, microstructure, and magnetic properties. The phase composition of RE11.8 alloys changes to a single 2:14:1 phase with increased wheel speeds. However, besides the 2:14:1 phase, the RE-rich phase can still be detected in RE16.1 alloys after increasing the wheel speeds. For ribbons prepared at 20 m/s, annealing promotes the generation of ultrafine primary grains in the RE11.8 alloys and subsequent grain growth, which leads to an increase and then a decrease in the coercivity of the alloys in the temperature range from 500 °C to 800 °C. The RE16.1 alloys consist of two phases after annealing, wherein the magnetic isolation of the RE-rich grain boundary phase relative to hard magnetic grains results in higher coercivity compared to the RE11.8 alloy. The preference of Y to enter the main phase grains rather than the RE-rich grain boundary phase leads to a decrease in the coercivity of RE16.1 alloys after annealing. These results provide new insights into the design and the development of Y-substituted Nd-Fe-B alloys.