Effect of yttrium addition on the glass forming ability of Co-based alloys

Abstract Cobalt-based amorphous alloy ribbons were prepared by means of melt-spinning. The effect of addition of a rare earth element yttrium on the glass forming ability (GFA) and thermal stability were investigated by X-ray diffraction analysis and differential scanning calorimetry. The results show that a small amount of yttrium is effective in improving the glass forming ability and thermal stability of a Co – Fe – Zr – Nb – B alloy. As-quenched glassy ribbon containing 4 at.% yttrium shows the highest GFA and thermal stability. The glass transition temperature T g , reduced glass transition temperature T rg , supercooled liquid region Δ T x , GFA parameter γ and Vickers hardness are 886 K, 0.618, 96 K, 0.423 and 1158 respectively. Crystallization kinetic studies show that the crystallization activation energies for (Co 45 Fe 21 Zr 4 Nb 10 B 20 ) 96 Y 4 glassy ribbon are as high as 826 kJ mol − 1 for the first crystallization peak. The excellent GFA and thermal stability of Y-containing alloy is mainly attributed to the scavenging of oxygen and large mismatch in atomic size induced by the addition of yttrium.