Studies on the formability of Al-based metallic glasses/nanocomposites based on isochronal DSC analysis

The Al86Si0.5Ni4.06Co2.94Y6Sc0.5 metallic glass of highly improved glass-forming ability (GFA) has been investigated by isochronal differential scanning calorimetry measurements, as well as the Al85Ni5Co2Y8 for comparison. The experimental results indicate that the Al86Si0.5Ni4.06Co2.94Y6Sc0.5 exhibits enlarged temperature interval between the first and second crystallization onsets (termed as primary fcc-Al/glass region), as well as enlarged second activation energy (Ep2) against the nucleation and the growth of intermetallic compounds besides fcc-Al. The variation of the Avrami exponent demonstrates that the primary crystallization process is a rapid two- and three-dimensional diffusion-controlled nucleation and growth mechanism initially, and the whole process is strongly controlled by the growth of fcc-Al crystals. According to the analysis on the basis of atomic mobility of alloy components, it demonstrates that the enlarged primary fcc-Al/glass region obtained through proper coexistence of dissimilar and similar elements would be in favor of preparing Al-based metallic glasses or nanocomposites in greater size.