Primary crystallization of Al–Ni–RE amorphous alloys with different type and content of RE

The primary crystallization of Al87Ni6RE7 and Al85Ni6RE9 (RE = La, Ce, Nd and Y) amorphous alloys was investigated by X-ray diffraction and differential scanning calorimetry. With decreasing the atomic radius of RE, i.e., in an order of La > Ce > Nd > Y, the thermal stability first remains almost unchanged for RE = La and Ce, and then gradually decreases when RE changes through Nd to Y. Meanwhile, the supercooled liquid region gradually enlarges in the Al85Ni6RE9, but changes complicatedly in the Al87Ni6RE7. The primary phase consists of fcc-Al plus metastable phase(s) for RE = La and Ce in the Al87Ni6RE7 or single metastable phase for RE = La, Ce and Y in the Al85Ni6RE9, but only fcc-Al in the other alloys. Except the Al85Ni6Nd9 alloy whose primary crystallization process is interface-controlled in growth, the primary crystallization processes of the other alloys are diffusion-controlled. With increasing the content of RE, the thermal stability, supercooled liquid region and nucleation rate increase. Meanwhile, metastable phases are prone to precipitate.