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

The glass forming ability and thermal stability of the quenched amorphous p hase 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 t hermal stability of the quenched amorphous phase decreases with the additio n 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 ener gy for primary crystallization However, the enhanced thermal stability of t he quenched amorphous phase with the addition of Sr and Ba does not lead to easier glass formation. The critical thickness of the quenched ribbons wit h 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 result s reveal the different effects of atomic size on the glass forming ability and the thermal stability of the quenched;amorphous phase against crystalli zation.