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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 Tg, reduced glass transition temperature Trg, supercooled liquid region ΔTx, 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 (Co45Fe21Zr4Nb10B20)96Y4 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.