Nano-eutectic growth in Co-17.8 wt%Gd alloy ribbons and the magnetostrictive properties at different wheel speeds

Under near-equilibrium solidification conditions, the Co-17.8 wt%Gd eutectic alloy forms rod-like eutectic microstructure of (αCo) solid solution and Co17Gd2 compound. When the solidification condition is far from the equilibrium, the rapid growth of nano-eutectic in Co-17.8 wt%Gd alloy ribbons is realized by the single-roller techniques. The average granular size (d) of nano-eutectic in the center of ribbons varies with the increase of wheel speed (V), d = 510.36-25.51 V+0.44 V2. XRD results of ribbons at different wheel speeds indicate that, with the rise of wheel speed, the main peak of Co17Gd2 compound becomes more and more notable, whereas the main peak of (αCo) solid solution tends to reduce. Along the length direction, the Co-17.8 wt%Gd alloy ribbons have the negative magnetostrictive strain. The magnetostrictive strain enhances with the increase of wheel speed. At the wheel speed of 40 m/s, the magnetostrictive coefficient of ribbons is measured to be - 733 ppm at the magnetic field of 6 kOe. The influence of the wheel speed and the magnetic field on the maanetostrictive coefficient is discussed.