Evaluation of glass formation and critical casting diameter in Al-based metallic glasses

Abstract

Abstract Critical cooling rate R c 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 R c value, and Al 86 Ni 6 Y 4.5 Co 2 La 1.5 alloy, the best glass former in Al-based systems, holds the lowest R c of about 3.01 × 10 3 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 × 10 3 K/s to 0.83 × 10 3 K/s. Based on these calculations, the critical casting diameter D c for a certain Al-rich multi-composition could be predicted. Further, for the composition Al 86 Ni 6 Y 4.5 Co 2 La 1.5 , bulk glassy sample with D c up to 1.5 mm has been obtained, confirming the theoretical prediction.