Formation of amorphous oxide in Al82Ni13Zr5 and Al88Ni7Ca5 alloys

• The stability of amorphous oxide is different depending on the alloy composition.
• The stability of amorphous oxide in Al88Ni7Ca5 is higher than that in Al82Ni13Zr5.
• The presence of calcium ion in oxide stabilizes amorphous structure of the oxide.

Formation and thermal stability of amorphous oxide in Al82Ni13Zr5 and Al88Ni7Ca5 alloys during holding at 873 K have been investigated. The thickness of amorphous oxide layer upon heating up to 873 K is ∼8 nm in Al82Ni13Zr5, while ∼15 nm in Al88Ni7Ca5. After exposure for 15 h, the amorphous oxide still remains in Al88Ni7Ca5, indicating that the thermal stability of the amorphous oxide in Al88Ni7Ca5 is higher than that in Al82Ni13Zr5. Such a phenomenon is discussed from the points of view of structural stability and oxygen ion mobility in the crystalline and amorphous oxide phases.