Effect of long-term room-temperature storage on the structure and properties of glassy melt-spun Mg-Al-Ca alloys

The effects of 48 months storage at room temperature on the structure and p roperties of glassy melt-spun Mg-Al-Ca alloys has been determined. The resu lts show that while Knoop hardness does not differ significantly from value s obtained shortly after melt spinning, x-ray diffraction (XRD) shows consi derably stronger signals from alpha Mg present in the glassy matrix, detect ed only for the most dilute glass forming composition some months after mel t spinning. High-resolution electron microscopy (HREM) studies show the pre sence of nanocrystallites in the glassy matrix with interplanar spacings ma tching alpha Mg, and energy-dispersive spectroscopy (EDS) indicates the pre sence of Al and Ca within these nanocrystallites. Differential scanning cal orimetry (DSC) studies at 20, 40, and 80 K/min show evidence of two-stage c rystallization with the first stage starting at similar to 120 deg with a p eak at similar to 150 degrees C and the second stage peaking at similar to 250 degrees C. The significance of these results is discussed.