Effect of Co and Cu alloying on Nd-Fe-Al based bulk amorphous alloys

To improve the glass forming ability of the Nd70Fe20Al10 alloy, cobalt was substituted into the alloy by replacing neodymium. The results indicate that the glass forming ability of Nd70-xFe20Al10Cox (x = 0, 2.5, 5, 7.5, 10) increases with the addition of Co. Bulk amorphous Nd60Fe20Al10Co10 cylinders with a diameter of 3 mm and a length of 50 mm have been prepared by the copper mold casting method. Addition of copper into the Nd60Fe20Al10Co10 alloy by replacing neodymium, however, significantly reduces the glass forming ability. The bulk amorphous Nd60Fe20Al10Co10 and Nd59Fe20Al10Co10Cu1 alloys exhibit hard magnetic behavior, whereas melt-spun ribbons of the same compositions are magnetically softer. The addition of 1 at% Cu into the Nd60Fe20Al10Co10 alloy causes an increase in coercivity from 298 kAm(-1) to 321 kAm(-1). The tendency for amorphization of the Nd-Fe-Al based alloys will be discussed with respect to the reduction of the melting temperature and the enthalpy of mixing of the constituents upon alloying with Co or Cu, respectively.