Texturing hard Nd-Fe-B powdered ribbons in high magnetic field

Abstract

A new route to texture NdFeB alloys in magnetic field was presented in a recent paper [1], constituting an attempt towards the preparation of anisotropic bonded magnets. NdFeB ribbons composed of Nd2Fe14B grains embedded in a Nd-Cu eutectic matrix, were annealed under an applied magnetic field up to 16T, at temperatures above the Nd-Cu melting temperature. A crystallographic texture was found to progressively develop at annealing temperatures, above 700 °C. In this paper, it is proposed that the grain orientation mechanism involves a competition between the aligning magnetic field torque acting on the magnetic grains and thermal disordering effects which becomes more and more significant as the temperature is increased. A simple model is developed to evaluate these effects. It is shown as well that a lowering of the alloy coercivity takes place during annealing. © 2009 IOP Publishing Ltd.