MAGNETOSTRICTION OF MELT-SPUN DY-FE-B ALLOYS

The magnetostriction of melt-spun ribbons of Dyx(Fe 1-yBy)1-x (x=0.2, 0.25, 0.3; 0≤y≤0.2) alloys is systematically investigated as a function of the wheel speed during melt quenching. As the wheel speed increases from 10 to 50 m/s, the magnetic softness improves with the wheel speed rather continuously for the alloys with the Dy content x=0.2 and 0.25 but it exhibits a maximum at the wheel speed of 30 or 40 m/s for the alloys with the highest B content (x=0.3). The softness also improves with the B content for a fixed wheel speed. Homogeneous and ultrafine grain structure is observed for the first time even in the as-spun state when the ribbons of the alloy Dy0.3(Fe0.8B0.2) 0.7 are fabricated at the wheel speed of 30 m/s. The ribbon having the ultrafine grain structure exhibits good magnetic softness together with a high strain.