Magnetic Properties and Corrosion Resistance of Sintered Nd-Fe-B Magnet Caused by Er69Fe31 Alloy Grain Boundary Addition

TL;DR

This paper shows how adding a less expensive Er69Fe31 alloy improves the corrosion resistance of Nd-Fe-B magnets without significantly reducing their magnetic properties.

Contribution

The novel use of Er69Fe31 alloy as a cost-effective additive to enhance corrosion resistance in sintered Nd-Fe-B magnets.

Findings

Er69Fe31 alloy addition improves corrosion resistance with minimal impact on magnetic properties.

Er partially replaces Nd at grain edges, forming a low HA (Er,Nd)2Fe14B shell that reduces coercivity.

Different heat treatments affect magnet performance, suggesting potential for optimizing other rare earth applications.

Abstract

This work reports on the effect of the heavy rare earth element Er on Nd–Fe–B magnets by using a simple Er69Fe31 alloy additive, which is much less expensive than Dy and Tb elements. It was found that the corrosion resistance was improved with a minimal reduction in magnetic properties by rationally controlling the Er69Fe31 addition content. The main reason is that Er element partially replaces the Nd element at the edge of the main phase grain to form an (Er,Nd)2Fe14B shell with low HA, which leads to a decrease in coercivity. However, the improvement in the corrosion resistance is mainly due to the Er69Fe31 alloy addition, which slows down the corrosion rate. Simultaneously, an investigation was conducted into the different advantages that target magnets when subjected to diverse heat treatment methodologies. The above findings may lead to the development of applications for other rare earth elements, thereby accelerating the development of low-cost permanent magnets comparable to commercially available sintered Nd-Fe-B magnets.

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