Thermal stability and crystallization behavior of Al86Ni9Y5 amorphous alloys with different Si addition

Abstract

In this paper, a series of (Al 86 Ni 9 Y 5 ) 100- x Si x ( x = 0, 1, 2, 3, 4, 5) amorphous ribbons were prepared to study the effect of Si addition on the crystallization behavior. The amorphous microstructure of Al 86 Ni 9 Y 5 base alloy is essentially heterogeneous. When it is subjected to annealing, primary α-Al nanocrystals first precipitate in the Al-rich regions and then regrow in the residual amorphous matrix at a far higher temperature, resulting in two separate primary crystallization events, called as abnormal crystallization. Addition of Si to the base alloy principally enhances the chemical heterogeneity, due to which more α-Al crystals precipitates with a lower onset temperature and crystallization activation energy. Meanwhile this abnormal crystallization of α-Al is promoted when x ≤ 3. The largest temperature interval between two crystallization peaks of α-Al is up to 154 K. As more Si is added, however, the crystallization of Al 3 Ni and Al 3 Y is advanced, causing the vanishment of the abnormal crystallization. The strong interaction between different species of solute atoms and the existence of free Al atoms are responsible for the occurrence of the abnormal crystallization. • Abnormal crystallization of α-Al occurs in Al 86 Ni 9 Y 5 but not in Al 86 Ni 9 La 5 amorphous alloy. • Addition of 1–3 at.% Si enhances the abnormal crystallization in Al 86 Ni 9 Y 5 amorphous alloy. • Severe chemical heterogeneity is essential for the abnormal crystallization. • Strong interaction between solute atoms promotes the abnormal crystallization.