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(r) and H(ci)) 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.