Role of atomic size on glass formability and thermal stability of Al-based amorphous alloys

The glass forming ability and thermal stability of the quenched amorphous phase are evaluated in Al87Ni7Gd6-x(Ca, Sr, Ba)(x) alloys in terms of large atomic size effects of Alkali metals. Thermal analysis indicates that the thermal stability of the quenched amorphous phase decreases with the addition of Ca and increases with the addition of up to 2 at%Sr and Ba, as seen in the change of primary crystallization peak temperature and activation energy for primary crystallization However, the enhanced thermal stability of the quenched amorphous phase with the addition of Sr and Ba does not lead to easier glass formation. The critical thickness of the quenched ribbons with completely amorphous phase is found to decrease from 300 to 70 mum as the content of Alkali elements is increased at the expense of Gd. These results reveal the different effects of atomic size on the glass forming ability and the thermal stability of the quenched;amorphous phase against crystallization.