CORROSION BEHAVIOR AND MAGNETIC-PROPERTIES OF MELT-SPUN ND-(FE.CO.NI)-B-(AL.TI) RIBBONS

The corrosion behaviour of melt-spun Nd-Fe-B alloy ribbons in which Fe was replaced with Co and Ni and small quantities of Al and Ti added w as investigated from the viewpoint of anodic corrosion, Although the a ddition of Ni degraded the magnetic properties of melt-spun ribbons, i t improved corrosion resistance. According to EDXS and AES analyses, t he corrosion products on the surface of Ni-free ribbons consisted of N d and Fe oxides, but the Nd oxide corrosion product almost disappeared in the Ni-added samples. Also, the degradation of magnetic properties after the corrosion test was suppressed by the addition of Ni. From t hese results, it was thought that the improvement of corrosion resista nce and the smaller degradation of magnetic properties of Nd-(Fe.Co.Ni )-B-(Al.Ti) ribbons after the corrosion test were associated with the suppressed dissolution of the Nd-rich phase at the grain boundaries. T he oxidation of Ni-added melt-spun ribbons also showed similar charact eristics and behaviour to the corrosion test in the morphologies of th e ribbon surface and magnetic properties after the oxidation test.