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

The Al₈₆Si_0.5Ni_4.06Co_2.94Y₆Sc_0.5 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 Al₈₆Si_0.5Ni_4.06Co_2.94Y₆Sc_0.5 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 (E_p2) 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.