Crystallization behaviour and thermal stability of two aluminium-based metallic glass powder materials

The crystallization behaviour and thermal stability of two Al-based metallic glass powder materials, Al85Ni5Y6Co2Fe2 and Al86Ni6Y4.5Co2La1.5, have been investigated using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and electron microscopy. Both alloy powders show a distinct three-stage crystallization process with a similar gap of ∼75 K between the onset crystallization temperature (Tx) and the second crystallization temperature. Crystallization occurs by the precipitation and growth of fcc-Al, without intermetallic formation. The apparent activation energy for each stage of crystallization was determined from DSC analyses and the phases resulting from each crystallization stage were identified by XRD and electron microscopy. The critical cooling rate for each alloy powder was calculated from the DSC data. These results are necessary to inform the consolidation of amorphous powder particles of Al85Ni5Y6Co2Fe2 or Al86Ni6Y4.5Co2La1.5 into thick (>1 mm) metallic glass components.