Influences of Si addition on the thermal stability and crystallization behavior of Al-Y binary amorphous alloys

Highlights: • Minor Si was added to Al₉₀Y₁₀ amorphous alloy. • The primary crystallization of α-Al is split into two stages with 2.5 at% or more Si addition. • The Si addition depresses the precipitation of Al₄Y but promotes the formation of Al₃Y. • The Si addition stabilizes α-Al₃Y phase significantly. • The strong interaction between Si and Y resulted in the abnormal crystallization. -- Abstract: In the present study, the crystallization behavior of (Al₉₀Y₁₀)_100−xSi_x (x = 0, 1, 2, 2.5 and 3 at%) amorphous alloys were characterized by differential scanning calorimetry, X-ray diffraction and transmission electron microscopy. As Si is added to the Al₉₀Y₁₀ base amorphous alloy, the primary crystallization of α-Al is advanced to lower temperature, the precipitation of Al₄Y in the residual amorphous phase is depressed but the crystallization of Al₃Y is promoted. The Si addition stabilizes the α-Al₃Y phase significantly, due to which both the as-cast ingot and the fully crystallized ribbon of (Al₉₀Y₁₀)₉₈Si₂ alloy consist of α-Al and α-Al₃Y, whereas the corresponding products in Al₉₀Y₁₀ alloy are α-Al and β-Al₃Y. The addition of 2.5 at% Si makes the crystallization of α-Al split into two stages with a temperature interval of 140 K between the two peaks. The reason is thought to be related with the enhanced concentration fluctuation in amorphous alloy and the slower diffusion of Y atoms in crystallization after the Si addition.