Importance of chamber gas pressure on processing of Al-based metallic glasses during melt spinning

The effect of chamber gas pressure on the amorphicity of Al85Ni5Y10 alloy was studied for the melt-spinning process. The amorphicity of as-quenched ribbons was characterized by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The chamber atmosphere pressure is crucial to the cooling rate of melt spinning. At high vacuum, at pressure less than 0.001 atm, fully crystalline fragments are obtained. Monolithic amorphous ribbons were only obtained at a gas pressure of 0.1 atm, 0.2 atm or higher. The extended contact length between ribbons and the copper wheel contributes to the high cooling rate of melt spinning in Al-based glass forming alloys; that is supported by images recorded by a high-speed camera. Higher chamber pressure increases contact length between ribbons and the wheel, which is qualitatively elucidated by Bernoulli's equation.