Abstract: The Hf_15-xCo₇₈B₇W_x (x=0,1,2,3) alloy meltspun ribbons were prepared through the method of adding trace of W in Hf₁₅Co₇₈B₇ alloy. The magnetic properties, phase composition and microstructure were investigated by magnetic measurements, Xray diffraction (XRD), thermomagnetic analysis (TMA) and scanning electron microscope (SEM). The results show that proper addition of W can improve the coercivity （H_C） of Hf₁₅Co₇₈B₇  alloy significantly, 
 Hf_15-xCo₇₈B₇W₂  meltspun ribbons are composed of Co7Hf phase and a small amount of fccCo phase, W atoms enter the lattice of Co₇Hf phase, resulting in the decrease of the Curie temperature (T_C) of Co₇Hf phase and increase of the magnetocrystalline anisotropy field (H_a). The grain size of alloy decreases significantly.

Key words: Hf_15-xCo₇₈B₇W_x alloy ribbons, Co₇Hf phase, coercivity