Sm 2 (Co,Fe,Cu,Zr) 17 magnets for use at temperature ⩾400 °C

Abstract

Sintered Sm2(Co,Fe,Cu,Zr)17 magnets with improved high temperature performance have been obtained by reducing the iron content in the magnet alloys. A record intrinsic coercive force, HCI, of 8.3 kOe at 400 °C was obtained when the iron content was decreased to 7 wt%. At 400–600 °C, 2:17 magnets with low iron content have demonstrated lower irreversible loss of magnetic flux, higher maximum energy product, and lower temperature coefficient of HCI. A temperature coefficient of HCI=−0.12%/°C (20–400 °C) was obtained for the low Fe magnets, compared to −0.23%/°C for commercial 2:17. Reducing iron content increases both Curie temperature and anisotropy field. Therefore, it is anticipated that new 2:17 magnet materials capable of operating at 400 °C or higher temperatures can be developed by reducing or eliminating the iron content and making other adjustments in composition and heat treatment.