Effect of La content on the room temperature ageing behavior of Al 90− xNi 6La 4+ x ( x = 0–3) metallic glasses

Abstract

The ageing behavior of Al 90− x Ni 6La 4+ x ( x = 0–3) amorphous alloys under ambient temperature (20–50 °C) has been studied. Partial crystallization has been observed in all alloys after several years of ageing under ambient conditions especially in Al 90Ni 6La 4 and Al 89Ni 6La 5 alloys, where the onset of crystallization temperatures are comparatively lower. The transformations have been studied by differential scanning calorimetry, X-ray diffraction and transmission electron microscopy. These alloys showed two stages of crystallization upon heating. A significant decrease of first stage of crystallization enthalpy was observed after 5.5 years of room temperature ageing and showed a mixed structure containing fcc-Al nanocrystals (20–40 nm) in an amorphous matrix. The results are explained in terms of transformation kinetics at the ageing temperatures.