Effects of W substitution on the magnetic properties, phase evolution and microstructure of rapidly quenched Co80Zr18B2 alloy

The effects of a partial substitution of W for Zr on the magnetic properties, phase evolution, and microstructure of Co80Zr18−xWxB2 (x=0, 1, 2 and 3) melt-spun ribbons are investigated in this paper. For the as-spun samples, the optimal magnetic properties of iHc=6.6 kOe and (BH)max=4.5 MGOe are achieved in the Co80Zr16W2B2. Thermomagnetic analysis (TMA) and x-ray diffraction (XRD) results suggest that the as-spun Co80Zr16W2B2 mainly comprises of hard magnetic phase. Scanning electron microscope (SEM) results indicate that W addition refines the microstructure, which results in an increase in the intergrain exchange interaction. The effects of heat treatment on the magnetic properties of as-spun Co80Zr18−xWxB2 (x=0, 1, 2 and 3) are also studied. The maximum iHc of 7.3 kOe with a (BH)max of 3.8 MGOe is obtained in the Co80Zr16W2B2 after a heat treatment at 550 °C. The origin of coercivity enhancement in Co80Zr16W2B2 is ascribed to the increase in magnetocrystalline anisotropy field (Ha) of hard magnetic phase.