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Critical cooling rate Rc for a series of Al-based glass formers, as well as cooling rate T′ for copper-mold casting Al-based bulk metallic glass (BMG) samples, have been calculated. It is found that the glass forming ability (GFA) is reflected by the change of Rc value, and Al86Ni6Y4.5Co2La1.5 alloy, the best glass former in Al-based systems, holds the lowest Rc of about 3.01 × 103 K/s. The T′ for the rod sample is determined by casting diameter D. When synthesizing Al-based BMGs, with the D increases from 1 mm to 3 mm, the value of T′ decreases from 7.48 × 103 K/s to 0.83 × 103 K/s. Based on these calculations, the critical casting diameter Dc for a certain Al-rich multi-composition could be predicted. Further, for the composition Al86Ni6Y4.5Co2La1.5, bulk glassy sample with Dc up to 1.5 mm has been obtained, confirming the theoretical prediction. Keywords: Al-based bulk metallic glasses, Critical cooling rate, Copper-mold casting |
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