A high performance Nd-Fe-B magnet with improved corrosion resistance

Various alloy modifications have been examined in order to improve the corrosion resistance and temperature stability of Nd-Fe-B magnets. Such alloy modifications are generally accompanied by a reduction in magnetic properties. Therefore, modifications which satisfy the criteria for both high magnetic properties (B/sub r/ and H/sub cj/) and good corrosion resistance are desired. It is found that when the three elements Co, Al, and Zr are simultaneously substituted for Fe in Nd-(Dy)-Fe-B magnets, both the corrosion resistance and the magnetic properties are significantly improved. The optimum Zr content is about 1.0 wt.%. A long-term (100 days) corrosion test in an autoclave environment has not disintegrated or attacked the surface of some Nd-(Dy)-Fe-Co-B-Al-Zr magnets. This indicates that corrosion-free high-performance magnets can be readily produced from Nd-(Dy)-Fe-Co-B-Al-Zr.<
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