Relationship between the precipitation of face-centered cubic Zr2Ni phase and the stability of supercooled liquid state in Zr-Cu-Ni-Al metallic glasses

The crystallization processes of (Zr0.64Ni0.36)(100-x)Al-x (x = 5, 7.5 and 10) and (Zr0.64Ni0.36-0.0xCu0.0x)(95)Al-5 (x = 0, 6, 10, 13 and 16) metallic glasses were studied by using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). For the (Zr0.64Ni0.36)(100-x)Al-x (x = 5 and 7.5) and (Zr0.64Ni0.36-Cu-0.0x(0.0x))(95)Al-5 (x = 0, 6, 10 and 13) alloys, crystallization proceeds through double-stage exothermic reactions. The first exothermic reaction corresponds to the precipitation of a metastable face-centered cubic Zr2Ni (F-Zr2Ni). For the (Zr0.64Ni0.36)100-Al-x(x) (x = 10) and (Zr0.64Ni0.36-0.0xCu0.0x)(95)Al-5 (x = 16) alloys, crystallization proceeds through a single-stage exothermic reaction, corresponding to the precipitation of stable crystalline phases. Accompanying the above changes in crystallization mode, the supercooled liquid region DeltaT(x), defined as the temperature interval between the glass transition temperature T-g and the crystallization temperature T-x, increases from 39 K for (Zr0.64Ni0.36)(95)Al-5 to 64 K for the (Zr0.64Ni0.36)(90)Al-10 in (Zr0.64Ni0.36)(100-x)Al-x (x = 5, 7.5 and 10) alloy series, and from 39 K for (Zr0.64Ni0.36)(95)Al-5 to 70K for (Zr0.64Ni0.20Cu0.16)(95)Al-5 in the (Zr0.64Ni0.36-0.0xCu0.0x)(95)Al-5 (x = 0, 6, 10, 13 and 16) alloy series. The reason for the stabilization of the supercooled liquid state at higher Al concentrations in the (Zr0.64Ni0.36)(100-x)Al-x (x = 5, 7 5 and 10) alloy series and at higher Cu concentrations in the (Zr0.64Ni0.36-0.0xCu0.0x)(95)Al-5 (x = 0, 6, 10, 13 and 16) alloy series is discussed.