Mischmetal substitution in Nd2Fe14B sintered permanent magnets

Abstract

Neodymium-iron-boron based permanent magnets are the preferred magnets for motor applications because of their high energy production. However, the supply of neodymium is subject to high risks due to geopolitical and economical conflicts of interests. Cerium, lanthanum, and Mischmetal can be potential substitutes of neodymium as they have similar electronic structures as the neodymium, and more importantly, they are abundant and low-cost. One of the important properties of permanent magnets is coercivity, which defines the ability of the magnet to work in a demagnetization field. Coercivity depends on magneto crystalline anisotropy and microstructure. The microstructure at the grain boundaries in sintered 2:14:1 type magnet helps to remove defects and improve coercivity by reducing magnetostatic interactions between grains. Addition of nonmagnetic, low melting point alloys like PrCu to the magnetic material may prevent magnetic coupling of adjacent grains by forming continuous grain boundary layer. The microstructure can be further optimized through heat treatment. In this work, the effect of PrCu on the coercivity of Mischmetal substituted Nd-Fe-B sintered magnets, influence of sintering temperature on microstructure and magnetic properties are studied and the maximum amount of Mischmetal that can be utilized to achieve optimum energy production was identified.